DAMASCUS, Syria -- President Bashar Assad vowed Thursday that "Syria will defend itself" against Western military strikes over a suspected chemical weapons attack, and the U.N. said inspectors will leave within 48 hours carrying information that could be crucial to what happens next.
British Prime Minister David Cameron argued strongly for military intervention in Syria but was rejected in a preliminary vote in Parliament, while French defense officials said openly for the first time that their military is preparing for a possible operation. The Obama administration was briefing congressional leaders about its case for attacking Syria.
The U.S., Britain and France blame Assad's regime for the alleged chemical weapons attack Aug. 21 on rebel-held suburbs of Damascus. The Syrian government denies the allegations, saying rebels staged the attack to frame the regime.
At the United Nations, a meeting of the permanent members of the Security Council on the Syrian crisis ended after less than an hour after being convened by Russia, a staunch ally of the Assad regime.
As Western leaders made their case at home for intervening in Syria's 3-year-old civil war, Assad remained defiant.
"Threats to launch a direct aggression against Syria will make it more adherent to its well-established principles and sovereign decisions stemming from the will of its people, and Syria will defend itself against any aggression," he said in comments reported by the Syrian state news agency.
It's not clear whether Assad would retaliate against any attacks or try to ride them out in hopes of minimizing the threat to his continued rule. The U.S. has said regime change it not the objective of any military action it may carry out.
The U.N. experts have been carrying out on-site investigations this week to determine whether chemical weapons were used in the attack that the group Doctors Without Borders says killed 355 people. Inspectors visited the eastern suburb of Zamalka, where they interviewed survivors and collected samples.
Amateur video posted online showed U.N. inspectors in gas masks walking through the rubble of a damaged building. One inspector scooped pulverized debris from the ground, placed it in a glass container and wrapped the container in a plastic bag. The video corresponded to other AP reporting of the events depicted.
U.N. Secretary-General Ban Ki-moon urged Western powers to hold off on any military action until the experts can present their findings to U.N. member states and the Security Council. Speaking in Vienna, Ban said the U.N. team is to leave Syria on Saturday morning and will immediately report to him. He also said that he spoke to President Barack Obama about ways to expedite the U.N. probe.
Some of the experts will take samples to laboratories in Europe after leaving Damascus, according to U.N. spokesman Farhan Haq, adding that the team's final report will depend on the lab results and could take "more than days."
The mandate of the U.N. team is to determine whether chemical agents were used in the attack, not who was responsible. But Haq suggested that evidence collected by investigators -- including biological samples and interviews -- might give an indication of who was behind the attack.
"Their mission is to determine whether chemical weapons were used. It's not about attribution. At the same time, I would like to point out that they will have large number of facts at their disposal -- they have collected a considerable amount of evidence through samples, evidence through witness interviews -- and they can construct from that evidence of a fact-based narrative that can get at the key facts of what happened on the 21 of August," Haq said.
British and American leaders -- who have put the blame for the attack squarely on the regime's shoulders -- faced pushback against possible punitive military strikes, particularly before the investigators release their conclusions.
In a stunning defeat Thursday night, Cameron's government lost a preliminary vote calling for military strikes. Although nonbinding, the rejection means Cameron's hands are tied and he released a terse statement to Parliament saying it was clear to him that the British people did not want to see military action.
The vote lost 285-272 and the prime minister said he would respect the will of the House of Commons.
At the start of the week, Cameron had seemed ready to join Washington in possible military action against Assad. But the push for strikes against the Syrian regime began to lose momentum as Britain's Labour Party announced its opposition to the move.
Cameron promised to give the U.N. inspectors time to report back to the U.N. Security Council and try to secure a resolution there. He also promised to give lawmakers a second vote in a bid to assuage fears that Britain was being rushed into an attack on Assad.
It wasn't enough, however. Suspicions lingered that what was billed as a limited campaign would turn into an Iraq-style quagmire.
Obama also was trying to shore up political support for a move against Syria. The administration planned briefings for leaders of the House and Senate and national security committees, U.S. officials and congressional aides said.
Obama, although still reportedly weighing his options, signaled Wednesday the U.S. was moving toward a punitive strike, saying he has "concluded" that Assad's regime is behind the attacks and that there "need to be international consequences."
U.S. intelligence officials said the intelligence linking Assad or his inner circle to the Aug. 21 attack is no sure thing, with questions remaining about who controls some of Syria's chemical weapons stores and doubts about whether Assad ordered the strike.
The administration has signaled that it would act against the Syrian government even without the backing of allies or the U.N.
French defense officials said publicly for the first time that their military is preparing for a possible operation in Syria -- but President Francois Hollande stopped short of announcing armed intervention.
Unlike Obama and Cameron, he has a freer hand to decide how to deal with the crisis -- Hollande does not need parliamentary approval to launch military action that lasts less than four months.
French Defense Minister Jean-Yves Le Drian said "the armed forces have been put in position to respond" if Hollande commits French forces to an international intervention.
France has a dozen cruise missile-capable fighter aircraft at bases in the United Arab Emirates and the Horn of Africa nation of Djibouti. France's military was at the forefront of the NATO-led attacks on Libyan dictator Moammar Gadhafi in 2011, and led an intervention against extremists in Mali earlier this year.
The U.S. has already dispatched naval forces toward the eastern Mediterranean toward Syria's shores. If Obama decides on military action, U.S. administration and defense officials in recent days have said the most likely move would be the launch of Tomahawk missiles off ships in the Mediterranean.
Syrian officials have urged the U.N. inspectors to extend their mission to investigate what the regime alleges are three chemical attacks against Syrian soldiers this month in the Damascus suburbs.
Haq, the U.N. spokesman, said the U.N. team will leave despite the government's request, although the appeal is being given serious consideration and that the experts intend to return to Syria to investigate other incidents.
The brief meeting of the Security Council permanent members was the second time in two days they had met on Syria.
In a tension-filled meeting Wednesday, the U.S., Britain, France, China and Russia discussed a resolution proposed by Britain to authorize the use of military force against Syria. Moscow firmly opposes military action.