Syria's Assad making gains, Kerry admits

US Secretary of State John Kerry admitted Wednesday that Syrian President Bashar al-Assad was making gains on the ground, but he 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.

But asked whether he believed that America's policy in the war-torn country, which has seen a mounting death toll in its three-year conflict, had failed, he replied "No."

"The policy in Syria is just very challenging and very difficult," he added.

Earlier this week, the State Department denied reports Kerry told US lawmakers in a private meeting that he believed it was time to change strategy in Syria, where some 1360,000 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 told CNN.

"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 reevaluating whether there's more we can do, should do."