Donald Trump was not speaking literally when he made the unsubstantiated claim that former President Barack Obama wiretapped his New York skyscraper, the White House press secretary has said.

Mr Trump tweeted on March 4 that he had found out that "Obama had my 'wires tapped'" during the election and compared it to the "Nixon/Watergate" scandal.

Since then, neither the president or any member of his administration has provided any evidence to back up the claim.

On Monday, White House spokesman Sean Spicer said Mr Trump was not using the word wiretapping literally, noting that the president had put the term in quotation marks.

"The president used the word wiretap in quotes to mean broadly surveillance and other activities," Mr Spicer said.

He also suggested Mr Trump was not accusing the former president specifically, but instead referring to the actions of the Obama administration.

Mr Trump has not commented on the matter since his March 4 tweets.

He wrote: "Is it legal for a sitting President to be 'wire tapping' a race for president?"

In two other tweets, Mr Trump described Mr Obama tapping his phones, but did not put the phrases in quotation marks.

A spokesman for Mr Obama described the accusations as "simply false".

The US justice department has asked for more time to provide evidence to back up Mr Trump's claim.

The House intelligence committee said it would give the department until March 20 to comply with the evidence request.

That is the date of the committee's first open hearing on the investigation into Russia's interference in the 2016 election and possible contacts between Trump associates and Russia.

Possible Russian interference in the US election is being investigated. Credit: AP

A spokesman for the committee's Republican chairman said if the justice department does not meet the new deadline, the panel might use its subpoena power to gather information.

In its response, the justice department said it needed extra time to "review the request in compliance with the governing legal authorities and to determine what if any responsive documents may exist".

The president's accusations came amid numerous political questions surrounding his associates' possible ties to Russia.

The FBI is investigating Mr Trump's associates' contacts with Russia during the election, as are House and Senate intelligence committees.

The White House has asked those committees to also investigate Mr Trump's unverified wiretapping allegations against Mr Obama.