AP Source: Trump aide in frequent contact with Russia envoy

FILE - In this Sept. 6, 2013 file photo, Russia's ambassador to the U.S. Sergey Kislyak, speaks with reporters in Washington. The Obama administration is aware of frequent contacts between President-elect Donald Trump’s top national security adviser Michael Flynn and Russia’s ambassador to the United States, including on the day President Barack Obama hit Moscow with sanctions in retaliation for election-related hacking, a senior U.S. official said Friday, Jan. 13, 2017. (AP Photo/Cliff Owen, File) (The Associated Press)

FILE - In this Nov. 14, 2016 file photo, Sean Spicer arrives at Trump Tower in New York. The Obama administration is aware of frequent contacts between President-elect Donald Trump’s top national security adviser Michael Flynn and Russia’s ambassador to the U.S., including on the day President Barack Obama hit Moscow with sanctions in retaliation for election-related hacking, a senior U.S. official said Friday, Jan. 13, 2017. (AP Photo/ Evan Vucci, File) (The Associated Press)

FILE - In this Dec. 12, 2016 file photo, National Security Adviser-designate Michael T. Flynn waits for an elevator in the lobby at Trump Tower in New York. The Obama administration is aware of frequent contacts between President-elect Donald Trump’s top national security adviser Michael Flynn and Russia’s ambassador to the United States, including on the day President Barack Obama hit Moscow with sanctions in retaliation for election-related hacking, a senior U.S. official said Friday, Jan. 13, 2017. (AP Photo/Kathy Willens, File) (The Associated Press)

A senior U.S. official says the Obama administration is aware of frequent contacts between President-elect Donald Trump's top national security adviser and Russia's ambassador to the United States.

The official says the contacts happened on the day President Barack Obama expelled dozens of Russian officials from the U.S. and imposed sanctions as punishment for election-related hacking. The official says the administration is also aware of contacts between Trump adviser Michael Flynn and Ambassador Sergey Kislyak at other times as well.

The day after Obama announced sanctions, Russian President Vladimir Putin said he would not retaliate. Trump praised him for his restraint.

Flynn's conversations were first reported by Washington Post columnist David Ignatius. The official was not authorized to confirm the contacts publicly and spoke on condition of anonymity.