Donald Trump meets Russian foreign minister Sergey Lavrov one day after firing FBI chief James Comey

Donald Trump will meet Vladimir Putin's senior diplomat at the White House on Wednesday in a signal that US relations with Russia have improved.

The US president recently described them as being at an "all-time low" but his talks with Sergey Lavrov mark the highest level, face-to-face contact with Russia of the American leader's term in office.

Mr Trump's talks with Moscow's foreign minister will take place after the Russian's meeting earlier in the day with US Secretary of State Rex Tillerson.

A Russian plan to stabilise Syria after more than six years of civil war is the most urgent foreign policy topic on the agenda.

But the meeting will be impossible to separate from the Trump administration's unfolding political drama in Washington.

FBI and congressional investigations are looking into possible collusion between Trump campaign associates and the Kremlin related to last year's presidential election.

US intelligence agencies accuse Moscow of meddling to help Mr Trump's chances of victory.

The stigma of the Russia investigations has been impossible for Mr Trump to shake.

The president on Tuesday abruptly fired FBI Director James Comey, dramatically ousting the nation's most senior law enforcement official in the middle of the bureau's investigation into Mr Trump's ties with Russia.

Less than a month into Mr Trump's presidency, he sacked his national security adviser, Michael Flynn.

The president said Mr Flynn misled senior administration officials about his pre-inauguration talks with Sergey Kislyak, Russia's ambassador in Washington.

In a Senate hearing on Monday, former acting attorney general Sally Yates said she warned the White House in January that Mr Flynn "essentially could be blackmailed" by the Russians because he apparently had lied to his bosses about his contacts with Mr Kislyak.

Mr Trump has said he has no ties to Russia and is not aware of any involvement by his aides in any Russian election interference.

He calls the various investigations a "hoax" driven by Democrats still bitter that their candidate, Hillary Clinton, was defeated last year.

But in the meantime, his hopes for a possible rapprochement with Moscow, so regularly repeated during the campaign, have been derailed.

Relations soured further in April after the US blamed Syria's president Bashar Assad, a key Russian ally, for a deadly chemical weapons attack on civilians and Mr Trump fired some 60 cruise missiles at a Syrian air base in response.

After Mr Tillerson visited Mr Putin and Mr Lavrov in Moscow on April 12, Mr Trump said: "Right now we're not getting along with Russia at all."

Mr Lavrov will be coming to the American capital with a Russian plan to end the violence in Syria, after hashing out an agreement with Iran and Turkey last week.

The Russian diplomat has not visited Washington at all since 2013, a year before Russia's annexation of Ukraine's Crimea region and two years before it intervened militarily in Syria to help Assad remain in power.

AP