By the CNN Wire Staff

U.S. Secretary of State Hillary Clinton said Sunday that "the days are numbered" for Syrian President Bashar al-Assad's regime.

"There is no doubt that the opposition is getting more effective in their defense of themselves and in going on the offense against the Syrian military and the Syrian government's militias," Clinton said during a press conference in Tokyo on Sunday.

And with a recent increase in defections from the al-Assad regime, "the sand is running out of the hourglass," Clinton said.

"The sooner there can be an end to the violence and a beginning of a political transition process, not only will fewer people die, but there's a chance to save the Syrian state from a catastrophic assault that would be very dangerous not only to Syria but to the region," she said.

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