The Kremlin has weighed in on the Michael Flynn furore by saying Donald Trump's National Security Adviser did not discuss lifting Russian sanctions in a call with the ambassador.

Flynn allegedly held secretive phone calls with Russian ambassador Sergey Kislyak before Trump stepped into the Oval Office in which he promised the easing of sanctions imposed by Barack Obama.

If he did, that would put him in breach of the 1799 Logan Act, which bans private citizens from negotiating with foreign powers that are in dispute with the US.

But Kremlin spokesman Dmitry Peskov said Flynn and Kislyak had not discussed sanctions on Moscow in the phone call as the Kremlin announced Vladimir Putin and Trump could meet before the G20 summit in July.

Michael Flynn (right) allegedly spoke to Russian ambassador Sergey Kislyak out of turn in December

The two leaders have never met, but both have said they want to try to mend battered US-Russia ties, which fell to their lowest level since the Cold War after Moscow's 2014 annexation of Ukraine's Crimea.

The new US administration is under pressure over Russia with Flynn struggling to get past the controversy caused by the call.

When asked about it on Monday, Kremlin spokesman Dmitry Peskov told a conference call with reporters that Flynn and Kislyak had not discussed lifting sanctions on Moscow.

'Obviously every ambassador informs the centre (Moscow) about all the contacts he has so the information gets to us, but we are not willing to comment on internal discussions being held in Washington,' Peskov said.

Asked if there had been talks between any Russian and U.S. representatives on easing sanctions, Peskov said: 'We have already said there have not been any such talks.'

House Minority Leader Nancy Pelosi of California who wants Flynn suspended

House minority leader Nancy Pelosi demanded on Friday Donald Trump's national security adviser, Lt Gen Michael Flynn, be suspended and lose his intelligence clearance until an FBI investigation into his actions is concluded.

In a statement, Pelosi demanded that the Lt Gen be suspended and restricted from accessing intelligence until the FBI's investigation into his call is concluded.

'President Trump's kowtowing to Vladimir Putin is endangering our national security and emboldening a dangerous tyrant,' she said. 'What do the Russians have on President Trump that he would flirt with lifting sanctions and weakening NATO?

'The President and his National Security Advisor have given the Russians the impression that whatever they do, they are not to worry, because the Trump White House will not stand against their aggression.

'General Flynn should be suspended and have his intelligence clearance revoked until the facts are known about his secret contacts with the Russians.'

Flynn is alleged to have made the phone call on December 29, the day that Barack Obama imposed sanctions on Russia in response to Russian interference in the presidential election.

The accusations against Flynn emerged in January, and were subsequently denied by Vice President Mike Pence.

'They did not discuss anything having to do with the United States' decision to expel diplomats or impose censure against Russia,' Pence told CBS News's 'Face the Nation' on January 15.

The claims were addressed again in a Washington Post report on Thursday, in which 'senior US officials' interpreted Flynn's statements to Kisalyak as 'inappropriate and potentially illegal' promises of an easing in sanctions.

Flynn denied the claims twice in an interview on Wednesday, but on Thursday he told the Post through a spokesman 'that while he had no recollection of discussing sanctions, he couldn't be certain that the topic never came up.'

The FBI confirmed on Wednesday that they are currently investigating Flynn.

In her statement, Pelosi also demanded an FBI investigation into the wider 'financial, political and personal ties between President Donald Trump and Russia.'

And she added that 'Congress must also launch an bipartisan, independent, outside commission' into 'Russia's on the election and this Administration.'

She said that Republicans, like Democrats, should be 'alarmed' at the 'mortifying coziness the Trump Administration has shown with Putin.'

Vladimir Putin (pictured) and Donald Trump could meet before the G20 summit in July

On Friday Flynn's top deputy, Robin Townley, was fired from National Security Council after being denied security access by the CIA.

It's unclear why Townley's request for 'Sensitive Compartmented Information' clearance was rejected.

But Flynn and his allies believe it was motivated by Townley's skepticism at the intelligence community's techniques, sources told Politico.

The Logan Act was created as a result of George Logan's unauthorized negotiations with France in 1798, and enacted by President John Adams in 1799.

Those found guilty of breaking it can face imprisonment for up to three years, and be made to pay a fine.

Only one person has ever been indicted for violating the act: Francis Flournoy, a Kentucky farmer who, in 1803, wrote an article suggesting a separate Western nation allied with France. He was never actually prosecuted.