MOSCOW - 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.

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

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