WASHINGTON: The directors of the FBI and NSA are to give keenly awaited testimony before Congress Monday on what ties President Donald Trump may have with Russia and his explosive allegation that he was wiretapped by his predecessor Barack Obama.

Federal Bureau of Investigation Director James Comey and Mike Rogers of the National Security Agency will speak publicly for the first time about two issues that have riveted the American public for weeks and further divided the country's two ever-at-odds political parties.

The stakes for the tycoon-turned-world-leader could hardly be higher.

Comey will testify before the House Intelligence Committee at a hearing aimed at probing Russia's interference in the 2016 election campaign. Rogers is also scheduled to testify.

Trump and his entourage's possible ties with the Russia of President Vladimir Putin have been the subject of much speculation since before he was elected on November 8.

US intelligence agencies in January took the extraordinary step of stating publicly that they had concluded that hackers working for Russia broke into the email accounts of senior Democrats and released embarrassing ones with the aim of helping Trump defeat Hillary Clinton.

Even since then, the question of whether Trump and company were or are somehow in cahoots with Russia has dominated the national conversation.

A congressional panel so far has found no evidence that Trump's campaign colluded with Russia, its chairman said Sunday.

Based on "everything I have up to this morning -- no evidence of collusion," by Trump's team and Moscow, Representative Devin Nunes, chairman of the House Intelligence Committee, told Fox News.

Moscow has denied involvement in the hacks, and Trump has denounced the tumult over alleged Russia connections as a "total witch hunt."

Monday's hearing was also expected to address a second explosive issue: Trump's unsubstantiated accusations that the Obama administration wiretapped his phone at Trump Tower in New York during the campaign.

Trump on March 4 tweeted that Obama had "tapped" his phone -- a charge that has consumed political debate in the US capital.

Several congressional panels have launched investigations into Russia's alleged interference, including the House and Senate intelligence committees, which have jurisdiction over the nation's 17 intelligence agencies, and the House and Senate judiciary committees.

The FBI is also probing Russian interference in the election.

The question remains whether the agency has opened a criminal investigation into possible ties between Trump campaign aides and Russian officials.

Monday's hearing promises to be a very public showdown between the FBI and lawmakers, with the national security world certain to watch whether Comey drops a political bombshell.

Members of Congress have expressed frustration over what they call the lack of cooperation from the FBI about Russia and Trump's wiretap claim, which Obama and an array of other officials have flatly denied.

The issue of wiretapping first surfaced last month, when Trump's national security adviser Michael Flynn was forced to resign after it was revealed he had misled top officials over his contacts with the Russian ambassador to Washington to discuss sanctions Obama had just announced against Russia over the election hacking.

Around the same time, The New York Times reported that US intelligence had intercepted calls showing that members of Trump's campaign had repeated contacts with top Russian intelligence officials in the year preceding the election.

Nunes has said that the intelligence committee probe focuses in part on who revealed that Flynn had unreported private contacts with the Russians over the sanctions issue.

Adding to the intrigue, Trump's attorney general Jeff Sessions recused himself from any Russia-related inquiries after it was learned that he had met twice with the Russian ambassador in the months before Trump took office, and had failed to disclose this during his confirmation hearing when asked a question about such contacts and speaking under oath.

Domestically, the controversy over the wiretapping claim has pulled attention away from Trump's effort to push through other key items on his agenda, including the planned repeal of Obama's healthcare law, tax reform and his controversial travel ban.

Critics say it has also debased the already coarse tone of political debate in Washington and eroded the president's credibility at home and abroad.

Some of the fallout has been international in scope: The White House was forced to retract a charge repeated last week by its spokesman Sean Spicer suggesting that Britain's intelligence services aided the Obama administration in the alleged wiretap. That claim has strained relations with America's closest ally.

Still, as recently as Friday, Trump repeated the claim in an aside during a White House press conference with Angela Merkel.

"As far as wiretapping, I guess, by this past administration, at least we have something in common, perhaps," Trump told the German chancellor, referring to a WikiLeaks report in 2015 that the US had monitored calls involving Merkel and her top aides for years.

Copyright AFP (Agence France-Press), 2017