U.S. President Barack Obama called on his successor, Donald Trump, to push back against Russia when it deviates "from our values and international norms."
He made the call in Berlin on November 17 at a joint news conference with German Chancellor Angela Merkel.
Trump, who will take office on January 20, has signaled a potentially more conciliatory approach to Moscow.
In recent years, ties with Washington have plummeted toward Cold War-era lows as the two nations clash over Ukraine, Syria, and other issues.
Obama told reporters he hoped Trump was "willing to stand up to Russia where they are deviating from our values and international norms."
Following a telephone conversation with Russian President Vladimir Putin on November 14, Trump said he looked foward to "to having a strong and enduring relationship with Russia and the people of Russia."
However, some prominent Republicans in Congress, including Senator John McCain, have warned Trump against trying to ease ties with the Kremlin.
With reporting by AP and Reuters