The chances of Donald Trump being impeached are very slim, according to analyst at Japanese investment bank Nomura.

The US president is facing enormous scrutiny amid growing concerns in Washington regarding the relationship between Trump's team and Russia.

"This issue is unlikely to be resolved anytime soon, but impeachment risk seems low," Nomura analysts said.

"Removing Trump will require a two-thirds majority in the Senate and the chances of Republicans voting to impeach their own president seem low."

Last week, Trump fired FBI Director James Comey while the bureau investigated his campaign's alleged ties to Russia and it later emerged he had disclosed classified information about military operations involving Isis during a meeting with the Russian Foreign Minister at the White House.

On Wednesday night (17 May), the US Justice Department confirmed the appointment of former FBI chief Robert Mueller as special counsel for the investigation on the relationship between Trump and Moscow.

Earlier, Texas Democrat Al Green had become the first member of Congress to go to the House floor calling for Trump to be impeached, citing the mounting scandal over Trump's ties with Russia as proof Moscow interfered in last year's presidential elections.

The political turmoil has rocked the US markets, with the Dow and S&P 500 hitting their worst drop since September and the Nasdaq suffering its biggest decline since June on Wednesday.

Over the last two sessions, meanwhile, the dollar has lost all the gains it recorded following Trump's election in November last year and the Japanese investment bank expects the trend to continue.

"Increasing doubts over President Trump's ability to proceed with his economic policies will likely hurt US dollar momentum for the time being, even though expectations for bold US economic policy had already declined before this," analysts said.

Some bookmakers, however, consider the chances of an impeachment more concrete. Paddy Power Betfair offer odds of 3/1 – 25% of probability – on Trump being impeached this year, with those odds lengthening to 5/1, 16/1 and 33/1 in 2018, 2019 and 2020 respectively.

Odds on Trump's being impeached in the first term, however, are evens, which means the bookmaker believe there is a 50% chance of it happening. Bet 365, instead, has an impeachment at 11/10, giving a 47.6% chance.