US President Barack Obama says he hopes President-elect Donald Trump can stand up to Russia when needed and take a constructive approach to cooperating with Moscow where interests aligned.

“In order for us to solve many big problems around the world, it is in our interest to work with Russia,” Mr Obama told a joint news conference with German Chancellor Angela Merkel on Thursday.

“My hope is that the president-elect coming in takes a similarly constructive approach, finding areas where we can cooperate with Russia where our values and interests align, but that the president-elect also is willing to stand up to Russia when they are deviating from our values and international norms,” Mr Obama said.

This meant, he said, refraining from taking a “Realpolitik approach” and cutting deals that could “hurt people or … violate international norms … leave smaller countries vulnerable, or create long-term problems in regions like Syria”.

He added it was important for sanctions imposed against Russia over its actions in eastern Ukraine to remain in place until Moscow complied with the Minsk peace agreement.

On the issue of cyber attacks, Mr Obama said there was a difference between “Russian intelligence-gathering” and “meddling with elections or going after private organisations or commercial entities”.

He said he had “delivered a clear and forceful message that … we’re monitoring it carefully and we will respond appropriately if and when we see this happening”.

He also had a warning for young people, saying, “do not take for granted our systems of government and our way of life … Democracy is hard work”.

German Chancellor Angela Merkel and Barack Obama on his last trip to Europe. Photo: Getty

“If we are not serious about facts and what’s true and what’s not particularly in an age of social media … If we cant discriminate between serious arguments and propaganda, then we have problems.”

Mr Obama, asked if he thought Ms Merkel should run for a fourth term as chancellor, said he considered her an outstanding leader and would vote for Ms Merkel, if he were a German citizen.

He also said he planed to come back to Germany at least one more time — to visit Munich’s annual Oktoberfest.

“It’s wonderful to be back in Berlin. This is my sixth visit to Germany, it will not be my last,” Mr Obama told the news conference.

“I have somehow continued to miss Oktoberfest so that’s probably something that is better for me to do as a former president rather than as president. I’ll have more fun,” he said.