Never rule out anyone becoming the US president. If nothing else, that's surely what Donald Trump's extraordinary path to the White House has taught the world.

So step forth the next implausible candidate for the 2020 US presidential election – Stephen Colbert.

It was after downing shots of vodka on a Russian TV chat show that the US comedian announced he was thinking about running.

"I am here to announce that I am considering a run for president in 2020, and I thought it would be better to cut out the middle man and just tell the Russians myself," Colbert said to laughter and applause from the audience on late-night show Evening Urgant.

In a dig at possible collusion between Trump's campaign team and the Kremlin, he added: "If anyone would like to work on my campaign in an unofficial capacity, please just let me know."

Taking cues from Trump's bombastic style, The Late Show host finished with what could be his campaign slogan: "A strong America, a strong Russia."

Host Ivan Urgant raised a shot glass to the announcement, saying: "I'd like to make a toast to the beautiful country of the USA, which invented the internet. Thanks to it, we can meddle with US elections."

He went on to support Colbert's potential presidential run, saying: "To you, Stephen. Good luck. We'll do everything possible to make sure you get elected."

Colbert is no political virgin. In 2007 in announced he would be running in the presidential election the following year.

He kept up the claim for about a month before finally saying he was dropping his plans due to the expense involved.

The satirist is just the latest celebrity to make tongue-in-cheek announcements on wanting to replace Trump as president in 2020.

Last month, Dwayne "The Rock" Johnson jokingly told Saturday Night Live that he would be running with fellow actor Tom Hanks.

"I didn't think I was qualified at all, but now I'm actually worried that I'm too qualified," quipped Johnson.

Colbert is currently in Russia filming for his show, the Hollywood Reporter said.

After Donald Trump tweeted a message on Thursday claiming that he "did not make, and do not have" tapes or recordings of his conversations with former FBI director James Comey, Colbert responded by sharing a photo of him walking past The Hermitage Museum in Saint Petersburg.

He wrote alongside: "Don't worry, Mr. President. I'm in Russia. If the "tapes" exist, I'll bring you back a copy!"