The US president told reporters, "Both sides need to stop fighting and move towards a resolution through future negotiations."

"What I'm saying is, they need to stop fighting now, go home, stop killing people.

Otherwise, it's going to be difficult to discuss the final solution in detail," Donald Trump said.

"I think 78 percent of the land is occupied by Russia. Leave it where it is now. You can discuss it later," he said.

Ukraine has previously insisted that it will take back all of its territory.

Trump himself said last month that Ukraine could be defeated militarily and take back all of the territory occupied by Russia, including the Crimean peninsula and other areas of eastern Ukraine.

Trump is scheduled to meet with Russian President Vladimir Putin in Hungary in the next few weeks, but the exact date of the meeting has not been announced.