(CNN) -- Western powers on Thursday were debating using military power against Syria's government to counter a chemical weapons attack in Damascus' suburbs last week.
On Wednesday, U.S. President Barack Obama said there's no doubt that Syria launched chemical weapons attacks against its own people. Syrian President Bashar al-Assad's regime has blamed the August 21 attack on rebels.
-- The United States may have to take unilateral action against Syria after British lawmakers voted down a proposal for military action, a senior U.S. official said.
-- British Prime Minister David Cameron was dealt a blow Thursday in his push for a strong response, including possible military action, against Syria after the House of Commons rejected the measure.
-- The vote, 285-to-272, came just minutes after members of Parliament voted down a Labour Party motion calling for additional time for U.N. weapons inspectors to gather evidence over whether al-Assad's forces used chemical weapons in suburban Damascus.
-- A closed-door meeting of the U.N. Security Council ended with no agreement on a resolution to address the crisis in Syria, a Western diplomat told CNN's Nick Paton Walsh on condition of anonymity. "It was clear there was no meeting of minds, and no agreement on the text. It is clear that our approaches are very different and we are taking stock (of the next steps)," the diplomat said.
-- Members of the Security Council expect U.N. weapons inspectors to brief Secretary-General Ban Ki-moon shortly after they depart Syria on Saturday. Ban, in turn, will swiftly brief the Security Council on the findings, the diplomat said.
-- Cameron opened the emergency session of the House of Commons on Syria Thursday by saying the debate is about "how to respond to one of most abhorrent uses of chemical weapons in a century" -- not about regime change or invasion.
-- Cameron told the House of Commons that the UK government would not act without first hearing from U.N. weapons inspectors, giving the United Nations a chance to weigh in and Parliament to have a vote.
-- But ultimately, failing to act would give al-Assad a signal that he could use such weapons "with impunity, Cameron said.
-- The British government on Thursday published a summary of its intelligence assessment on Syria's alleged chemical weapons use, arguing that at least 350 people died in an attack in the Damascus area on August 21, and that there is no plausible culprit other than the Syrian government. It is "highly likely" that the Syrian government was behind the attack, the report said.
-- The British government also published its legal reasoning for a strike on Syria Thursday, saying that it would be justified on humanitarian grounds.
-- "The use of chemical weapons by the Syrian regime is a serious crime of international concern, as a breach of the customary international law prohibition on use of chemical weapons, and amounts to a war crime and a crime against humanity," the UK government's statement read. "However, the legal basis for military action would be humanitarian intervention; the aim is to relieve humanitarian suffering by deterring or disrupting the further use of chemical weapons."
-- British members of parliament received an open letter from the Syrian government Thursday, urging them not to take any military action against Syria, the press office for House of Commons Speaker John Bercow said.
-- The Syrian letter to British lawmakers compares the current situation to the march to war against Iraq a decade ago, and riffing on Shakespeare, saying: "If you bomb us, shall we not bleed?" It also says an attack on Syria would be illegal, and "would automatically strengthen our common enemy, al Qaeda and its affiliates."
-- Al-Assad vowed Thursday to defend against any Western military attack. "The threats of launching an aggression against Syria will increase its commitments," and "Syria will defend itself against any aggression," he said, according to Syrian state TV.
-- U.N. inspectors entered the eastern part of the Ghouta region outside Damascus on Thursday, Syrian activists said. The Ghouta area was hit by the August 21 attack, activists say.
-- Al-Assad's claim that rebels were behind the August 21 chemical attack is impossible, Obama said on "PBS NewsHour" Wednesday. "We do not believe that, given the delivery systems, using rockets, that the opposition could have carried out these attacks," Obama said. "We have concluded that the Syrian government in fact carried these out. And if that's so, then there need to be international consequences."
-- Former U.S. Defense Secretary Donald Rumsfeld, who along with President George W. Bush helped send the U.S. military into action in Iraq and Afghanistan, told the Fox Business Network on Wednesday that the White House has yet to justify potential strikes in Syria.