MOSCOW, April 1 (Xinhua) -- Kremlin spokesman Dmitry Peskov said Tuesday that Russia and the United States are continuing talks to resolve the Ukraine conflict, calling it a "complex issue."

"We are continuing to maintain contact with the United States," Peskov said at a daily briefing, commenting on reported threats from the United States to impose additional sanctions on Russia's oil industry if ongoing peace talks fail to make substantive progress.

"This is a very complex issue," he added. "The resolution of the Ukraine conflict we are discussing now requires further efforts."

Earlier on Tuesday, Russian Deputy Foreign Minister Sergey Ryabkov said in an interview that Russia could not simply accept the U.S.-backed proposal on Ukraine, as it fails to address Russia's demands for resolving the root causes of the conflict