WASHINGTON (REUTERS, AFP, BLOOMBERG) - US President Donald Trump has defended his accusation that his predecessor Barack Obama had Trump Tower wiretapped last year before the election.

"Wiretap covers a lot of different things," Trump said in an interview with Fox News that aired on Wednesday night (March 15).

He said he based his claims at least partially on media reports by the New York Times and Fox News, and remained confident that information emerging in the coming weeks would vindicate his so-far unsubstantiated charge.

Trump told Fox he would submit some "very good stuff" to validate his claims and that he would consider speaking more fully about the allegations as soon as next week. He did not specify if he intended to present the evidence to Congress, the public, or some other entity.

"Let's see whether or not I prove it," Trump said. "I just don't choose to do it right now."

Trump, speaking at length about the controversy for the first time, pointed specifically to a New York Times story from January, which reported that US law enforcement and intelligence agencies were examining intercepted communications and financial transactions as part of a broad investigation into links between the Russian government and Trump officials. But the story said it wasn't clear the intercepted communications had anything to do with Trump or his campaign.

The president also said he had seen a mention of wiretapping during a segment of the Fox News show Special Report with Bret Baier, but didn't specify what report he was specifically referring to.

Although he tweeted specifically that Obama had tapped his phone, he said he intended generally to allege that the prior administration had undertaken "surveillance and many other things."

Earlier on Wednesday, US House Intelligence Committee Chairman Devin Nunes, a Republican, said that his panel has not received any evidence that Trump was wiretapped during the 2016 presidential campaign.

"As I told you last week about the issue with the president talking about tapping Trump Tower, that evidence still remains the same, that we don't have any evidence that took place," Nunes told reporters.

"In fact, I don't believe just in the last week of time, the people we've talked to, I don't think there was an actual tap of Trump Tower," he said. "Are you going to take the tweets literally? And if you are, then clearly the president was wrong," Nunes added.

White House press secretary Sean Spicer on Tuesday said Trump's tweets weren't meant to be taken literally since the president could have been referring to a broad range of surveillance activity. "He doesn't really think that President Obama went up and tapped his phone personally," Spicer said.

FBI chief James Comey reportedly urged the Justice Department to denounce Trump's claim because of a lack of evidence, but the department has not done so.

Instead, the Justice Department requested on Monday for more time to turn over evidence relating to Trump's claim to the House Intelligence Committee, which initially set a Monday deadline.

On March 4, Trump sparked a furor when he wrote on his @realDonaldTrump Twitter account that Obama had tapped into communications at Trump Tower. "Terrible! Just found out that Obama had my 'wires tapped' in Trump Tower just before the victory. Nothing found. This is McCarthyism!"

"Is it legal for a sitting President to be 'wire tapping' a race for president prior to an election? Turned down by court earlier. A NEW LOW!" he added in a second tweet. The tweets sparked enormous controversy, in part because it is unprecedented for any US president to accuse a predecessor of a felony crime.

Obama's spokesman said Trump's wiretapping accusation is "simply false". "A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice," Obama spokesman Kevin Lewis said in a statement.

"As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any US citizen," said Lewis.

Since then, the White House has been under mounting pressure from the Capitol requesting evidence that the phones at Trump Tower were tapped.

"I think the president has one of two choices: either retract or to provide the information that the American people deserve, because, if his predecessor violated the law, President Obama violated the law, we have got a serious issue here, to say the least," John McCain, Chair of the Senate Armed Services Committee, said on Sunday.