MOSCOW -- Reaching a peace agreement on Ukraine will be a long road involving complex details, Kremlin Spokesperson Dmitry Peskov said on Saturday.

"It is clear that the American side is in a hurry, but the issue of a settlement in Ukraine is too complex," Peskov said in an interview with Russia's state television VGTRK, while commenting on Washington's possible retreat from mediation on the Ukraine issue.

Resolving the US conflict with Iran would be as difficult as resolving the Ukraine crisis, said Peskov, calling for patience in addressing existing conflicts.

His remarks came after US Secretary of State Marco Rubio reportedly said Washington would be willing to continue mediating Russia-Ukraine negotiations only if there is tangible progress.