WASHINGTON (Reuters) - President Donald Trump said on Friday he did not remember much about a meeting last year with a former campaign aide who pleaded guilty last month as part of a federal probe into alleged Russian meddling in the 2016 U.S. election.

Asked about a meeting in which aide George Papadopoulos suggested arranging a meeting with Russian President Vladimir Putin, Trump told reporters: “I don’t remember much about that meeting. It was a very unimportant meeting.”

According to court documents filed by Special Counsel Robert Mueller, Papadopoulos said at the meeting of foreign policy advisers in March 2016 “that he had connections that could help arrange a meeting between then-candidate Trump and President Putin.”

A photograph posted on Trump’s Instagram account shows Papadopoulos sitting at the same table with Trump as well as Jeff Sessions, now Trump’s attorney general, and several others.

Papadopoulos has pleaded guilty to lying to Federal Bureau of Investigation agents about contacts with people who claimed to have ties to top Russian officials, in the first criminal charges alleging links between the Trump campaign and Moscow. His plea was made public this week.

Sessions is under pressure from Senate Democrats to testify again about the Trump campaign’s Russia contacts. In testimony to the Senate Judiciary committee, Sessions has denied knowing anything about contacts between the campaign and Russians or Russian government intermediaries.

The president spoke before leaving for a trip to Asia, where his domestic woes are expected to dog him. Trump denies any collusion with Russia and Moscow denies interfering in the 2016 election.

Sessions is also under pressure from his boss, who has made clear he thinks the Department of Justice should look into his former presidential rival, Hillary Clinton, and her campaign’s behavior with the Democratic National Committee during the presidential primary race.

Trump told reporters on Friday that many people were unhappy with the Department of Justice, including him.

George Papadopoulos (3rd L) appears in a photograph released on Donald Trump's social media accounts with a headline stating that the scene was of his campaign's national security meeting in Washington, D.C. U.S. on March 31, 2016 and published April 1, 2016. Social Media/Handout via REUTERS

Those comments followed remarks he made during “The Larry O’Connor Show” on WMAL radio in which he lamented not having more say in the department’s work.

“The saddest thing is, because I am the president of the United States, I am not supposed to be involved with the Justice Department. I’m not supposed to be involved with the FBI. I’m not supposed to be doing the kind of things I would love to be doing. And I am very frustrated by that,” he said.

Trump on Friday repeated his urgings that the Justice Department and FBI investigate Clinton.

“Everybody is asking why the Justice Department (and FBI) isn’t looking into all of the dishonesty going on with Crooked Hillary & the Dems,” he said on Twitter.

His comments elicited criticism from several U.S. senators.

“President Trump’s pressuring of the Justice Department and FBI to pursue cases against his adversaries and calling for punishment before trials take place are totally inappropriate and not only undermine our justice system but erode the American people’s confidence in our institutions,” Republican Senator Bob Corker, who has frequently sparred with Trump, said in a statement.

Democratic Senator Dianne Feinstein said: “We can’t allow ourselves to become numb to the president of the United States calling on independent law enforcement organizations to investigate his political opponents. That’s characteristic of authoritarian regimes, not democracies, and it needs to stop.”

Trump has expressed frustration repeatedly over the Russia investigation, which has overshadowed his administration, at times referring to it as a “hoax” and a “witch hunt.”

Federal investigators this week charged Trump’s former campaign manager Paul Manafort and another ex-aide, Rick Gates, with money laundering and other crimes. In a court filing on Friday, Mueller estimated he would need three weeks to present his case against Manafort and Gates if it went to trial.

Both men pleaded not guilty.

Manafort’s attorney Kevin Downing said in a filing on Friday that he would challenge what he called “evidence improperly obtained by search warrant, subpoena or otherwise.” FBI agents seized documents and other material from Manafort’s Virginia home in a July raid.

(This version of the story was corrected to say that Papadopoulos pleaded guilty in October, not November in paragraph one)