U.N. experts who collected samples from last week’s alleged chemical weapons strike outside Damascus left Syria for the Netherlands on Saturday, hours after President Barack Obama said he is weighing “limited and narrow” action against the Syrian regime his administration blames for the attack.

In Moscow, Russian President Vladimir Putin urged Obama not to rush into a decision. The Russian leader said he was convinced the attack was a provocation carried out by those who want to draw the U.S. into the conflict, but that Washington should show any evidence to the contrary to the United Nations inspectors and the U.N. Security Council.

“If there is evidence it should be presented,” Putin said. “If it is not presented, that means it does not exist.”

Russia is one of Syrian President Bashar Assad’s staunchest allies. Putin’s comments were his first on the crisis since the suspected chemical weapons attack on rebel-held suburbs of Damascus on Aug. 21.