US Secretary of State John Kerry admitted Wednesday that Syrian President Bashar al-Assad was making gains on the ground, but denied US policy in Syria was failing.
"It's fair to say that Assad has improved his position a little bit, yes. But he's still not winning. This is a stalemate," Kerry told CNN television in an interview.
He was adamant, however, that America's policy had not failed in the war-torn country, despite a mounting death toll in thes three-year conflict.
"The policy in Syria is just very challenging and very difficult," Kerry added.
Earlier this week, the State Department denied reports Kerry told US lawmakers in a private meeting that it was time to change strategy in Syria, where some 136,000 people have died and millions have fled their homes.
"I don't want to make any excuse whatsoever. We want this to move faster. We want it to do better," Kerry said.
"But the point I'm making is that diplomacy is tough, slogging, slow work and hard work."
January marked the deadliest month so far in the conflict with some 6,000 dead, and Kerry said the United States was "always in the process of re-evaluating whether there's more we can do, should do."
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US President Barack Obama has so far refused to provide heavy weaponry to the moderate rebels battling to topple Assad, amid fears it could fall into the hands of militant groups flooding into the country.
Kerry pledged the administration would work with Congress as well as internally to come up with ways to push the Russians to use their influence on Assad in order to improve conditions on the ground.
And the top US diplomat, who has in the past advocated a more robust US policy on Syria, warned that "we don't have years" to find a way to end the war.
The United States is providing non-lethal support to the rebels, such as body armor, communications equipment and night-vision goggles.
"I don't want to go into details, I'm not free to go into all the details, but I will say to you that the president has taken an aggressive position," Kerry said.
He also pointed to a deal hammered out with Russia on eliminating Syria's chemical weapons stock as "a significant milestone" in getting rid of the "grotesque tool" the Assad regime had used against its own people.
The White House, meanwhile, repeated a message for Syria to "live up to its commitment" to help destroy all its chemical weapons arsenal after Damascus missed two deadlines for transporting the stockpile to a Syrian port.
"Russia has said it expects the Assad regime to deliver a substantial portion of its chemical weapons stockpile in the relatively near future. And we obviously believe that's very important," White House spokesman Jay Carney said.