Washington: US Secretary of State Hillary Clinton has termed as "troubling" and "frustrating" Russia's lack of cooperation in efforts to resolve the political and humanitarian crisis in Syria.

"It is a very troubling and frustrating situation because the Russians continue to say, oh, they're for humanitarian aid, but then they don't produce any plan that Assad will sign off on," Clinton told members of the House Foreign Affairs Committee."We are doing everything we can think of to influence the Russians and the Chinese, particularly the Russians -- they're the ones with the very deep, long-standing relationship with the Assad family, with Syria," she said.

Russia and China have twice vetoed UN Security Council resolutions on Syria that they believe could lead to a military operation that would repeat "the Libyan scenario".

Russia has also opposed calls to establish air corridors in Syria to provide humanitarian aid to civilians suffering from the consequences of clashes between troops loyal to President Bashar al-Assad and opposition forces.

Clinton expressed hope that Russia would finally agree to cooperate with the international community as it could be key to resolving "a terrible crisis that demands the entire world's attention".

"We know that if we can persuade them to work with us, at least on the humanitarian issue, they will have access to Assad that hardly anybody else does have, at least nobody in the West," she said. Syria has been the scene of anti-government protests for nearly a year.

According to the UN, more than 7,500 people have died in the unrest.