WASHINGTON — A senior Obama administration official said Friday that the United States was encouraged by the initial inventory that the Syrian government had submitted of its chemical weapons arsenal.

“We were pleasantly surprised by the completeness of their declaration,” said the official, who declined to be identified because he was not authorized to speak publicly on the matter.

“It was better than expected,” he added.

The Organization for the Prohibition of Chemical Weapons, the watchdog group known as the O.P.C.W. that oversees the international agreement banning poison gas, said on Friday that Syria had provided “an initial declaration” of its chemical weapons program.

The submission met the first deadline for Syrian compliance that was set down by the framework agreement that the United States and Russia concluded in Geneva last weekend.