The US has ended co-operation with Russia in the Syrian peace talks.

America says Vladimir Putin has backtracked on several issues they believed had been solved.

Russia has been accused of aiding pro-government troops in Aleppo, and of targetting civilians.

A joint press conference between the US Secretary of State, John Kerry, and the Russian Foreign Minister, Sergei Lavrov, has been cancelled.

The American decision followed the suspension by Moscow of a Russia-U.S. deal on the disposal of weapons-grade plutonium. 

President Vladimir Putin's decree cited Washington's "unfriendly actions".

Under the agreement, Russia and the US were to dispose of enough weapons-grade plutonium for about 17,000 nuclear warheads.