Michael Flynn. Kevin Hagen/Getty Images On Monday, Politico reported that Michael Flynn, the retired general and national security adviser to President Donald Trump, would advise the Trump administration to back Montenegro's entrance into NATO — a move that surely would infuriate Russia.

Flynn has longstanding ties to Russia — most notably, he was paid to attend a gala event for Russia Today, a Russian propaganda outlet. On that occasion, he dined with Russian President Vladimir Putin.

The Wall Street Journal reported in January that US counterintelligence agents investigated Flynn's ties to Russia. Recently, a group of top Democratic lawmakers urged the Department of Defense to do the same.

Throughout his campaign and presidency, Trump has repeatedly questioned the NATO alliance and the US's adversarial relationship with Russia.

Despite that, the US Senate Foreign Relations Committee has backed Montenegro's NATO bid for over a year. During this time, the small Balkan nation faced increasing pressure from Russia — including a failed coup in October that may be tied to Moscow.

A special prosecutor in Montenegro said in November that Russian nationalists tried to sway the country's October election with a plot to kill Milo Djukanovic, the Western-leaning prime minister.

"The organizers of this criminal group were nationalists from Russia whose initial premise and conclusion was that the government in Montenegro led by Milo Djukanovic cannot be changed in election and that it should be toppled by force," Milivoje Katnic, special prosecutor for organized crime in Montenegro, said at the time.

Flynn's backing of Montenegro's entrance into NATO would seemingly fly in the face of Trump's proposal to try to befriend Russia, as Russia sees NATO expansion as aggression against its interests.

Jorge Benitez, a senior fellow and NATO expert at the Atlantic Council, told Politico, "No NATO candidate country has ever faced such a dire attack or threat in the process of finishing its membership into the alliance."

However, Flynn is not alone among Trump appointees in striking a more hawkish tone toward Moscow. The US's ambassador to the UN, Nikki Haley, also signaled such an approach, saying on Thursday, "The dire situation in eastern Ukraine is one that demands clear and strong condemnation of Russian actions."

Russia officially denies a military presence in eastern Ukraine, where fighting has recently reignited.

Before Montenegro could join NATO, its accession bid must be approved by all 28 current NATO states and two-thirds of the US Senate.