The chairman of the US Senate Armed Services Committee has said President Donald Trump needs to give more information to the American people and Congress about his wiretapping accusations against predecessor Barack Obama.
Republican Senator John McCain told reporters: “The dimensions of this are huge. It’s accusing a former president of the United States of violating the law. That’s never happened before.”
Without providing any evidence, Mr Trump on Saturday made the explosive claim that Mr Obama had tapped his telephones during last year’s election.
The White House said Congress’ intelligence committees should investigate but declined to say more.
FBI Director James Comey privately asked the Justice Department to dispute the claim because he believed the allegations were false.
When asked whether Mr Trump accepted Mr Comey’s view, White House deputy press secretary Sarah Huckabee Sanders told ABC’s Good Morning America: “I don’t think he does.”
Mrs Sanders and Kellyanne Conway, another top adviser, said the president still firmly believes the allegations he made on Twitter over the weekend.
The aides said any ambiguity surrounding the issue is all the more reason for Congress to investigate the matter.
“We’d like to know for sure,” Mrs Sanders told NBC’s Today show.
The House and Senate intelligence committees, and the FBI, are investigating contacts between Mr Trump’s campaign and Russian officials, as well as whether Moscow tried to influence the 2016 election.
On Sunday, Mr Trump demanded that they broaden the scope of their inquiries to include Mr Obama’s potential abuse of executive powers.
When asked where Mr Trump was getting his information from, Mrs Sanders said the president “may have access to documents that I don’t know about”.
Likewise, Mrs Conway said that “credible news sources” suggested there was politically motivated activity during the campaign.
But Mrs Conway also said Mr Trump might have access to other information she and others do not.
“He is the president of the United States,” Mrs Conway told Fox News’ Fox & Friends.
“He has information and intelligence that the rest of us do not.”
Mr Trump is said to be frustrated by his senior advisers’ inability to tamp down allegations about contacts between his campaign aides and the Russian government.
Compounding the situation was the revelation last week that former US senator and now Attorney General Jeff Sessions, an early Trump campaign supporter, had met twice with the Russian ambassador but did not disclose that to lawmakers when he was asked about it during his Senate confirmation hearing.
Separately, an Indiana newspaper reported that Vice President Mike Pence used personal email to conduct state business when he was governor of Indiana.
The revelation recalled the use of personal email by Mr Trump’s 2016 opponent, Hillary Clinton, when she was secretary of state.
The issue dogged Mrs Clinton for most of the presidential campaign.
A US official told The Associated Press on Sunday that Mr Comey had asked the Justice Department to refute Mr Trump’s allegation of illegal wiretapping.
The department, however, has issued no such statement.
DoJ spokeswoman Sarah Isgur Flores declined to comment on Sunday, and an FBI spokesman also did not comment.
Senate Intelligence Committee Chairman Richard Burr said in a statement that the panel “will follow the evidence where it leads, and we will continue to be guided by the intelligence and facts as we compile our findings”.