WASHINGTON (AFP) - The United States plans to "follow up" with Russia to see whether a plan for Syria to hand over its chemical weapons is credible, a senior US official said on Monday.

But Mr Ben Rhodes, a US deputy national security advisor, told MSNBC that Washington would not ease pressure on Damascus and was wary of a "stalling" exercise.

Moscow earlier seized the diplomatic initiative by announcing a plan for Syria to put its chemical weapons under international control, which it said could forestall US air strikes.

"I think we will just have to follow up with them and with other countries going forward to assess the seriousness of this proposal," Mr Rhodes said.

"At the same time, it is going to be very important that we don't take the pressure off.

He said Washington would be interested in the Russian initiative "only if it is a credible proposal".

"What we don't want to have is another stalling exercise."