TOKYO—U.S. Secretary of State Hillary Rodham Clinton says time's running out on Syrian peace hopes and warns that the Syrian state could collapse.

Speaking in Japan, Clinton said Sunday that U.N. mediator Kofi Annan's acknowledgement that his peace plan is failing "should be a wake-up call for everyone."

She says last month was the deadliest for the Syrian people in the 16-month revolt against President Bashar Assad (bah-SHAR' AH'-sahd). Clinton adds that the opposition "is getting more effective in defense of themselves and going on the offensive against the Syrian military."

Clinton says Assad's regime must acknowledge that its days are numbered.

She says there's "still a chance to save the Syrian state from a catastrophic assault that would be very dangerous not only to Syria, but to the region."