WASHINGTON (REUTERS) - The United States is reviewing intelligence suggesting Syrian President Bashar al Assad's government may try to keep some chemical weapons instead of turning them all over for destruction, a US official said on Tuesday.

Under a Russian-US proposal, Syria agreed in September to destroy its chemical weapons program by mid-2014, averting a threat of US missile strikes.

"There are indications the Syrians may be intending to hold some of their stockpile in reserve," the US official said on condition of anonymity.

The official said it was important that the international community keep the Syrian government's "feet to the fire" to ensure that all Syrian chemical weapons are declared and destroyed.

"This development is not surprising. ... At this point, it's not derailing the diplomatic process," the official said.

The CIA and the Pentagon declined comment on the US concerns, reported earlier on Tuesday by CNN.