Speaker of the House Paul Ryan, meets with reporters during his weekly news conference on Capitol Hill in Washington, Thursday, May 10, 2018. (AP Photo/J. Scott Applewhite)

House Speaker Paul Ryan said Wednesday that President Donald Trump should not pardon himself, noting that no one in the United States is above the law.

Trump claimed Monday that he has "the absolute right to pardon myself," as Special Counsel Robert Mueller's year-long probe continues into possible collusion between Russia and Trump's 2016 election campaign, as well as possible obstruction of justice.

Asked by a reporter Wednesday if Trump does have that power, Ryan replied that he doesn't know the "technical answer" to the question.

"But obviously the answer is he shouldn't, and no one is above the law," said Ryan, a leading member of Trump's Republican Party.

Trump has taken an aggressive stance on his presidential powers in the probe, which he calls an unconstitutional "witch hunt." 

Most experts say his claims of the right to self-pardon, and accusation that the Mueller investigation is unconstitutional, lack strong legal foundation.

A January memo from Trump's legal team to Mueller asserted that a president has full power over Justice Department investigations and therefore cannot be charged with obstruction of justice. 

READ: Russia probe: 'I have the absolute right to pardon myself,' says Trump

On Monday the president wrote in a tweet: "As has been stated by numerous legal scholars, I have the absolute right to PARDON myself, but why would I do that when I have done nothing wrong?"

Ryan's comment was the most recent from Democratic and Republican politicians warning the president not to halt or stifle the Mueller investigation.

Ryan also rejected Trump's claim that FBI investigators illegally placed an informant inside his campaign.

After reviewing highly classified information last week, Republican Representative Trey Gowdy, chairman of the House Government Oversight Committee, dismissed the assertion that US agents targeted Trump.

"I have seen no evidence to the contrary of the initial assessment that Chairman Gowdy has made," Ryan said Wednesday.

"It would have been helpful if we got this information earlier," he added.

Mueller has already filed charges against 22 individuals and entities, including Russians and former members of Trump's campaign staff as well as his former national security advisor.

The investigation has so far made no allegations against the president himself.