President Barack Obama was meeting with his National Security Council on Friday morning on the alleged chemical weapons use by the Syrian regime last week.  Secretary of State John Kerry is scheduled to speak about Syria at the State Department at 12:30 p.m. Friday. He will reference the intelligence on Syria in his statement, and also speak to the U.S. response and the effort to build international support for possible action against the Syrian regime, according to a senior U.S. official.

The Obama administration will release declassified intelligence Friday backing up a government assessment that the Syrian regime was responsible for a chemical weapons attack, a senior administration official said.

This comes amid talk among major powers of a military response against the forces of Syrian President Bashar al-Assad. The administration has said that the information would be made public by the end of the week.

But diplomatic and political developments this week raised the chances of the United States going it alone in a military intervention.

A U.N. Security Council meeting on Syria ended in deadlock, and in the U.S. Congress, doubts about military intervention are making the rounds.

And the United States' closest ally, Great Britain, backed out of a possible coalition when its lawmakers voted down a proposal on military intervention.

British Prime Minister David Cameron said it is important for the United Kingdom to have a "robust response to the use of chemical weapons, and there are a series of things that (Britain) will continue to do."British involvement in a military action "won't be happening," he said.

But diplomacy is continuing. Speaking in televised comments aired Friday, Cameron said he expects to speak to President Obama over the "next day or so."

On Friday afternoon, U.N. Secretary-General Ban Ki-moon intends to consult with countries at the United Nations on developments in Syria and is scheduled to meet with permanent members of the U.N. Security Council at noon Friday.

U.S. Secretary of State John Kerry is scheduled to speak about Syria at the State Department on Friday at 12:30 p.m. ET.

Alone or together?

After the British vote, a senior U.S. official, speaking on condition of anonymity, told CNN that going it alone was a real prospect.

"We care what they think. We value the process. But we're going to make the decision we need to make," the official said.

Former President George W. Bush said Obama's "got a tough choice to make."

"I was not a fan of Mr. Assad. He's an ally of Iran, he's made mischief," he told Fox News on Friday. "If he (Obama) decides to use the military, he's got the greatest military in the world backing him up."

In a statement released Friday, former President Jimmy Carter said "a punitive military response without a U.N. Security Council mandate or broad support from NATO and the Arab League would be illegal under international law and unlikely to alter the course of the war."

A former director of the CIA says he believes Obama would face off with al-Assad alone.

"I can't conceive he would back down from a very serious course of action," retired Gen. Michael Hayden told CNN's Wolf Blitzer.

U.S. Defense Secretary Chuck Hagel's response to the vote was more diplomatic.

The United States respects the results, he told journalists in Manila, the Philippines. "Every nation has a responsibility to make their own decisions."

The United States will continue to consult with the British government and still hope for "international collaboration."

"Our approach is to continue to find an international coalition that will act together," he said.

The government of France supports military intervention, if evidence incriminates the government of using poison gas against civilians.

But on Friday, President Francois Hollande told French newspaper Le Monde that intervention should be limited and not include al-Assad's overthrow.



Public opinion

Skeptics of military action have pointed at the decision to use force in Iraq, where the United States government under Bush marched to war based on a thin claim that former dictator Saddam Hussein was harboring weapons of mass destruction.

Opponents are conjuring up a possible repeat of that scenario in Syria, though the intelligence being gathered on the use of WMDs in Syria may be more sound.

Half of all Americans say they oppose possible U.S. military action against Syria, according to an NBC News survey released Friday.

Nearly eight in 10 of those questioned say Obama should be required to get congressional approval before launching any military attack against al-Assad's forces

The poll, conducted Wednesday and Thursday, indicates that 50 percent of the public says the United States should not take military action against Damascus in response to the Syrian government's alleged use of chemical weapons against its own citizens, with 42 percent saying military action is appropriate.

But the survey suggests that if any military action is confined to air strikes using cruise missiles, support rises. Fifty percent of a smaller sample asked that question say they support such an attack, with 44 percent opposing a cruise missile attack meant to destroy military units and infrastructure that have been used to carry out chemical attacks.

"Only 25 percent of the American people support military action in Syria," former U.S. Ambassador to the United Nations Bill Richardson told CNN's Piers Morgan on Thursday.

Convincing evidence

To shake off the specter of the Iraq war, the public needs convincing that chemical weapons were used and that al-Assad's regime was behind it.

"You have to have almost incontrovertible proof," Richardson told CNN's Piers Morgan on Thursday.

It's there, said Arizona Sen. John McCain, and will be visible soon. He thinks that comparisons to Iraq are overblown and that doubts are unfounded.

"Come on. Does anybody really believe that those aren't chemical weapons -- those bodies of those children stacked up?" the Republican senator asked Morgan.

Al-Assad's government has claimed that jihadists fighting with the opposition carried out the chemical weapons attacks on August 21 to turn global sentiments against it.

McCain doesn't buy it.

"The rebels don't have those weapons," he said.

The president also needs to assure Congress that a possible intervention would not get out of hand, said Democratic Rep. Chris Van Hollen of Maryland.

"The action has to have a very limited purpose, and the purpose is to deter future use of chemical weapons," he said.

Haunted by Iraq

The parliamentarians in London shot down the proposal in spite of intelligence allegedly incriminating the Assad government.

Britain's Joint Intelligence Committee has concluded it was "highly likely" that Syrian government forces used poison gas outside Damascus last week in an attack that killed at least 350 people, according to a summary of the committee's findings released Thursday.

A yes vote would not have sent the UK straight into a deployment.

Cameron had said his government would not act without first hearing from the U.N. inspectors and giving Parliament another chance to vote on military action. But his opposition seemed to be reminded of the Iraq war.

"I think today the House of Commons spoke for the British people who said they didn't want a rush to war, and I was determined we learned the lessons of Iraq, and I'm glad we've made the prime minister see sense this evening," Labour Party leader Ed Miliband told the Press Association.

The no vote came after a long day of debate, and it appeared to catch Cameron and his supporters by surprise.

For days, the prime minister has been sounding a call for action, lending support to talk of a U.S.- or Western-led strike against Syria.

"I strongly believe in the need for a tough response to the use of chemical weapons, but I also believe in respecting the will of this House of Commons," the prime minister said.

"We will not be taking part in military action," Cameron said Friday. "The British Parliament has spoken very, very clearly," he said.

Though Cameron did not need parliamentary approval to commit to an intervention, he felt it important "to act as a democrat, to act a different way to previous prime ministers and properly consult Parliament," he said Friday.

He regrets not being able to build a consensus of lawmakers, he said.

Letter from al-Assad

Before the vote, Syria's government offered its own arguments against such an intervention. In an open letter to British lawmakers, the speaker of Syria's parliament riffed on British literary hero William Shakespeare, saying: "If you bomb us, shall we not bleed?"

But the letter also invoked Iraq, a conflict justified on the grounds that Iraq had amassed stockpiles of chemical and biological weapons and was working toward a nuclear bomb -- claims that were discovered to have been false after the 2003 invasion.

"Those who want to send others to fight will talk in the Commons of the casualties in the Syrian conflict. But before you rush over the cliffs of war, would it not be wise to pause? Remember the thousands of British soldiers killed and maimed in Afghanistan and Iraq, not to mention the hundreds of thousands of Iraqi dead, both in the war and in the continuing chaos."

British Commons Speaker John Bercow published the letter.

U.N. deadlock

Lack of support for military intervention at the United Nations on Thursday was less of a surprise.

Russia, which holds a permanent seat on the U.N. Security Council, is one of Syria's closest allies and is most certain to veto any resolution against al-Assad's government that involves military action.

Moscow reiterated the stance Friday.

"Russia is against any resolution of the U.N. Security Council, which may contain an option for use of force," Deputy Foreign Minister Gennady Gatilov said Friday.

A closed-door Security Council meeting called by Russia ended with no agreement on a resolution to address the growing crisis in Syria, a Western diplomat told CNN's Nick Paton Walsh on condition of anonymity.

U.N. weapons inspectors are now in Syria trying to confirm the use of chemical weapons. The inspectors are expected to leave the country by Saturday morning.

They are to brief U.N. Secretary-General Ban Ki-moon, who, in turn, will swiftly brief the Security Council on the findings.

Congressional jitters

The president is facing doubts at home as well: More than 160 members of Congress, including 63 Democrats, have now signed letters calling for either a vote or at least a "full debate" before any U.S. action.

The author of one of those letters, Democratic Rep. Barbara Lee of California, said Obama should seek "an affirmative decision of Congress" before committing American forces.

More than 90 members of Congress, most of them Republican, signed another letter by GOP Rep. Scott Rigell of Virginia. That letter urged Obama "to consult and receive authorization" before authorizing any such military action.

Congress is in recess until September 9.

White House spokesman Josh Earnest said Obama was still weighing a potential response to the chemical weapons attacks.

The president has said that he is not considering a no-fly zone and has ruled out U.S. boots on the ground in Syria.

Al-Assad has vowed to defend his country against any outside attack.

CNN's Barbara Starr, Elise Labott, Christine Theodorou, Holly Yan, Nick Paton Walsh, Jim Acosta, Max Foster and Bharati Naik contributed to this report.