Media playback is unsupported on your device Media caption President Trump told reporters it was unlikely he would be interviewed

US President Donald Trump has said it is "unlikely" he will be interviewed by Robert Mueller, the man investigating possible ties between the Trump presidential campaign and Russia.

There was no collusion, Mr Trump said, adding: "I'll see what happens."

In June 2017, Mr Trump said he would "100%" be interviewed under oath.

He has consistently denied that his campaign worked with Russia to undermine his opponent Hillary Clinton, calling the accusations a "witch hunt".

Earlier this week the US media reported that Mr Trump's lawyers were in talks with the Mueller investigation to set a date for an interview.

When asked about the specifics of the interview on Wednesday, Mr Trump criticised the FBI's investigation and its 2016 interview with Mrs Clinton for her use of a private email server while she was secretary of state.

"When you talk about interviews, Hillary Clinton had an interview where she wasn't sworn in, she wasn't given the oath, they didn't take notes, they didn't record and it was done on the Fourth of July weekend," Mr Trump said. "That's, perhaps, ridiculous, and a lot of people looked upon that as being a very serious breach."

What is the investigation?

US intelligence agencies believe Russia tried to sway the election in favour of Mr Trump and a special counsel - that's Robert Mueller - is looking into whether anyone from his campaign colluded in the effort. The charge is denied both by Russia and by the US president.

The special counsel has the powers of a US attorney, meaning he can subpoena records and bring criminal charges.

He can also prosecute anyone who interferes in his investigation through crimes including perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses.

If he decides to question Mr Trump, he may opt to do so on paper, through a voluntary investigation, or by issuing him with a subpoena to appear before a jury. The latter is the only option that would be compulsory for Mr Trump to attend.

Media playback is unsupported on your device Media caption What the world thinks of Trump

There are several ongoing investigations by the special counsel into Russian's alleged election interference.

Mr Mueller is looking into:

The Russian government's efforts to interfere in the election

Any links or co-ordination between Russia and Trump campaign-linked individuals

Any matters that arose or may arise directly from the investigation

Three congressional panels are also investigating Russia's alleged interference.

What has reaction been?

In recent weeks, tensions have been rising along party lines in Congress as Democrats claim Republicans are intentionally trying to undermine investigations into the president.

Why attacks on Mueller are mounting

The White House and many Republicans have argued claims of collusion are a political smear, devoid of credibility.

On Wednesday, Senator Dianne Feinstein, a California Democrat, released the transcript of an interview with the head of a Washington firm that commissioned a dossier on Mr Trump compiled by ex-British spy Christopher Steele.

Glenn Simpson, head of Fusion GPS, told a Senate committee that Mr Steele took his concerns that Mr Trump was being blackmailed by the Kremlin to the FBI in July 2016.

Mr Simpson defended the research file, which purported to show financial and personal links between Mr Trump, his advisers and Moscow.

The dossier was reportedly partially funded by Mrs Clinton's campaign and the Democratic party.

Democrats also made public a report on Wednesday showing the scope of Russian President Vladimir Putin's attempt to meddle in elections in both the US and Europe and undermine democracies worldwide.

The 200-page report directly called out Mr Trump, warning that, "never before in American history has so clear a threat to national security been so clearly ignored by a US president."

The report compared the Russia threat to Pearl Harbor and the 9/11 attacks, and commended the actions taken by former US presidents in uniting the country to combat major world threats.

What has the FBI investigation established so far?

It has come out that senior members of Mr Trump's team - including his son, Donald Jr, and the former National Security Adviser Michael Flynn - met Russian officials or alleged go-betweens, and some of the meetings were not initially disclosed.

Mr Flynn was charged after admitting to having made false statements to the FBI about meetings with Russia's ambassador as part of a plea deal. Some analysts have suggested that Mr Mueller may also be investigating if Mr Trump's handling of the Flynn affair amounted to an obstruction of justice.

Adviser George Papadopoulos has also admitted lying to the FBI about meeting with alleged Russian go-betweens.

In October, Mr Trump's former campaign manager, Paul Manafort, and his business associate Rick Gates were accused of conspiring to defraud the US in dealings with Ukraine. Both deny the charges, which centre on relations with a former Ukrainian president who was very close to Russia.