US President Barack Obama told Russian President Vladimir Putin on Monday that sanctions will remain in place until Moscow changes course on Ukraine.
"Until [the Minsk agreement on cessation of hostilities] is implemented, the US is not going to pull down sanctions," Obama said, calling for an agreement in the coming weeks after a meeting between the leaders on the sidelines of the Group of 20 summit in China.
He called talks with Putin on the matter "constructive, but not conclusive" and said it remains to be seen whether the Russian leader actually wants a solution or is comfortable with a constant, low-grade conflict on his border.
Putin said he had expressed willingness to find a solution to the conflict and to meet with Ukrainian President Petro Poroshenko.
Obama, German Chancellor Angela Merkel and French President Francois Hollande met earlier Monday and agreed to cooperate in pushing Russia to end its military incursion in Ukraine.
Earlier, Hollande announced on Facebook that preparations were under way for an international summit to discuss the conflict in Ukraine.
"We agreed to organize in the next few weeks a summit between Germany, France, Russia and Ukraine" Hollande said in the online post.
"In Ukraine, we need to continue the Minsk process and address current bottlenecks including the implementation of the special status, the security situation and the lack of trust between the parties," Hollande added.
Ukrainian troops have been fighting Russian-backed separatists in eastern Ukraine since 2014.