National security adviser General Michael Flynn delivers a statement daily briefing at the White House in Washington Feb. 1, 2017. Reuters

President Donald Trump's relationship with Russia made headlines again Thursday night after the Washington Post exclusively reported that National security adviser Michael Flynn went over U.S. sanctions against the Kremlin with Moscow's ambassador to Washington just weeks before Trump took office. The report came after months of critics slamming Trump's seemingly cozy relationship with the Kremlin.

It's unclear if Flynn promised Russian Ambassador Sergey Kislyak that the Trump administration would end sanctions imposed by the Obama administration in late December after intelligence officials said Moscow hacked Democratic officials during the 2016 election to help Trump win. Flynn repeatedly said this week that he did not discuss the sanctions with Kislyak. But his spokesman said Thursday that Flynn “indicated that while he had no recollection of discussing sanctions, he couldn’t be certain that the topic never came up.”

Kislyak, for his part, has said he enjoyed unchecked communication with Flynn via text message, by phone and in person. “It’s something all diplomats do,” he said.

Former officials in the Obama administration, however, expressed concern about the communications. “Kislyak was left with the impression that the sanctions would be revisited at a later time,” an unnamed former official told the Washington Post.

Flynn has other ties to Russia. He was once photographed sitting next to Putin at a lavish party in Moscow. He also visited Moscow in 2013 while serving as director of the Defense Intelligence Agency.

Vice President Mike Pence has denied that Flynn discussed the sanctions with Russia before entering the White House. "General Flynn has been in touch with diplomatic leaders, security leaders in some 30 countries. That’s exactly what the incoming national security advisor should do,” Pence told CBS anchor John Dickerson in January. “But what I can confirm, having spoken to him about it, is that those conversations that happened to occur around the time that the United States took action to expel diplomats had nothing whatsoever to do with those sanctions.”

Trump defended Vladimir Putin this week after a Fox News reporter called the Russian president "a killer." Trump answered: “There are a lot of killers. What, you think our country’s so innocent?”

"For an American president to suggest that his own country is as murderous as Russia is unprecedented, wrong and a gift to Moscow’s propagandists. And for Mr. Trump to think that Mr. Putin has much to offer America is a miscalculation not just of Russian power and interests, but also of the value of what America might have to give up in return," the Economist wrote Thursday. "Russian hacking may have helped Mr Trump at the polls, but that does not mean he can trust Mr Putin. The Kremlin’s interests and America’s are worlds apart."