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.

The United States and its allies 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 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 is 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.

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 and will immediately report to him. He also said 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 21st of August,” Haq said.

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.