Media playback is unsupported on your device Media caption Republicans have questions about Trump and his wiretap claim

US President Donald Trump has stood by his unsubstantiated claim that Barack Obama wiretapped Trump Tower last year.

He told Fox News a "wiretap covers a lot of different things" and hinted more could emerge in the coming weeks.

Mr Obama has denied the charge and former spy chiefs and several lawmakers have said they have seen no evidence.

The latest senior figure to cast doubt on the allegation was the Republican chairman of the House intelligence committee.

Devin Nunes said on Wednesday he doesn't believe "there was an actual tap of Trump Tower".

Earlier this month, Mr Trump tweeted that President Obama had wiretapped his phones during the presidential campaign.

In a series of tweets, he accused his predecessor directly, asking: "Is it legal for a sitting President to be 'wire tapping' a race for president?"

Image copyright Twitter

Image copyright Twitter

Talking to Fox News in an interview that was broadcast in full on Wednesday night, the president made his first comments about the wiretap accusation he made two weeks ago.

He said: "Wiretap covers a lot of different things. I think you're going to find some very interesting items coming to the forefront over the next two weeks."

Despite repeated requests from reporters, the White House has not provided any evidence to support the president's claim.

White House Press Secretary Sean Spicer has said Mr Trump "used the word 'wiretap' in quotes to mean broadly surveillance and other activities".

Image copyright Getty Images Image caption Mr Trump has produced no evidence to support his accusation

And he was not accusing Mr Obama personally, Mr Spicer said.

Mr Trump asked Congress to examine the allegation as part of an investigation into alleged Russian meddling in last year's election.

Senator Lindsey Graham, who is leading the Senate Judiciary Committee's investigation of allegations of Trump-Russia ties, has pressed the FBI to come forward with more details of its own probe into the issue.

Mr Graham said on Wednesday he would use a court order to force FBI Director James Comey to submit details on its Russian investigation and whether there was any evidence of Mr Trump's phones being wiretapped.

No evidence of wiretapping, according to:

former President Barack Obama

FBI Director James Comey

ex-Director of National Intelligence James Clapper

ex-CIA Director John Brennan

Republican chairman of House intelligence committee, Devin Nunes

Republican John McCain, who chairs Senate Committee on Armed Services

House Speaker Paul Ryan

Former White House Chief of Staff Denis McDonough

Mr Comey promised on Wednesday to provide answers in a classified briefing.

US intelligence agencies found that Russia conducted cyber-attacks against the Democratic Party as part of an effort to influence the election in Mr Trump's favour.

Russia has repeatedly denied any involvement.

Mr Trump has been dogged by claims that his advisers and staff had ties to Russian officials, but there has been no evidence of any collusion between his campaign and Moscow.