German Chancellor Angela Merkel says Russia must withdraw its troops from Ukraine for a peace plan there to work.

Merkel told Russian President Vladimir Putin in a phone call late Monday that the complete withdrawal must accompany a securing of the Russian-Ukrainian border to prevent fighters and arms flowing to pro-Russian separatists in eastern Ukraine.

She also welcomed talks between Russia, Ukraine and the European Union on free trade, and called for such trilateral talks to address the issue of natural gas deliveries from Russia to Ukraine.

Ukraine and the West have repeatedly contended that Russia is fueling the separatist uprising in eastern Ukraine with manpower, weapons and expertise, something that Moscow denies.

The cease-fire between rebels and Ukrainian troops took effect on Sept. 5 but has been violated repeatedly.