United States President Barack Obama on Thursday urged president-elect Donald Trump to stand up to Russia when it breaches international norms and not “just do whatever is convenient at the time”. While he said does not expect his successor to follow his strategy on Moscow, he emphasised that the US cannot ignore differences between the White House and Kremlin on Ukraine, Syria and other matters, AP reported.

“My hope is that he does not simply take a realpolitik approach,” Obama said, using a German reference for a foreign policy fueled by political benefit. The outgoing president, whose tenure ends in January, was speaking at a joint press conference with German Chancellor Angela Merkel in Berlin, during his farewell tour in Europe.

Obama further said that he was “cautiously optimistic” about Trump’s presidency, implying that the “solemn responsibilities” and “extraordinary demands” of the role may hold the businessman back from making incendiary comments, which marked his campaign trail. Merkel mirrored his stand, saying she would approach the Trump administration “with an open mind”.

The Republican won the US presidential elections on November 8 against Democratic rival Hillary Clinton. The former secretary of state, however, won in the popular vote, while Trump secured more than the requisite 270 electoral votes.

However, foreign policy adviser to Russian President Vladimir Putin, Yuri Ushakov, told Russian news agencies that Obama’s administration was “doing everything it can to drive bilateral ties into a deadlock” and insisted that they had the “shared desire” to combat terrorism in Syria. The US has accused Moscow of worsening the Syrian civil war by extending military support to President Bashar al-Assad.