Speaking at a news conference with Russian Foreign Minister Sergey Lavrov, Kerry noted that Assad said a 30-day lead time would be standard.
"There is nothing standard about this process," Kerry said, because Assad has used his chemical weapons.
"The words of the Syrian regime in our judgment are simply not enough."
Kerry cautioned that a U.S. military strike could occur if Assad doesn't agree to dismantle his chemical arsenal properly.
He said, "There ought to be consequences if it doesn't take place."
Lavrov said the dismantling "will make unnecessary any strike against the Syrian Arab Republic."