FILE - U.S. President Donald Trump gives remarks on tax cuts for American workers at the White House, Washinton, Apr. 12, 2018.
FILE - U.S. President Donald Trump gives remarks on tax cuts for American workers at the White House, Washinton, Apr. 12, 2018.

U.S. President Donald Trump said Monday the investigation into links between his 2016 campaign and Russia is "rapidly losing credibility."

In four Twitter comments, Trump belittled special counsel Robert Mueller's year-long criminal investigation into Moscow's meddling in the election and whether he obstructed justice by trying to thwart the probe a year ago when he fired FBI director James Comey, who was leading the investigation before Mueller was named to take it over.

In another tweet, he complained, "What a total mess. Our Country has to get back to Business!"

Trump noted the Republican-controlled House Intelligence Committee "found No Collusion, Coordination or anything else with Russia.

Trump was alluding to a court hearing Friday in Mueller's case against Paul Manafort, who for several months was Trump's campaign manager in the run-up to the election.

President Trump's former campaign manager Paul Man
President Trump's former campaign manager Paul Manafort (C) arrives at U.S. District Court for a motions hearing in Alexandria, Virginia, U.S., May 4, 2018.

Manafort has been charged with bank and tax fraud in connection with his lobbying efforts in Ukraine that predates Trump's run for the presidency, but Judge T.S. Ellis III in Virginia questioned whether Mueller had the authority to bring the case against Manafort.

"I don't see what relation this indictment has with what the special counsel is authorized to investigate," Ellis told prosecutors. "You don't really care about Mr. Manafort's bank fraud. ... What you really care about is what information Mr. Manafort could give you that would reflect on Mr. Trump or lead to his prosecution or impeachment."

Ellis later said: "The vernacular is to 'sing,' is what prosecutors use. What you got to be careful of is they may not only sing, they may compose."

But Ellis did not rule on Manafort's bid to dismiss one of the indictments against him.

Democratic leanings?

Trump has occasionally complained about the Democratic ties of Mueller's group of lawyers, although Justice Department rules forbid considering political affiliations in naming prosecutors. The Mueller lawyers include numerous attorneys with a breadth of experience in prosecuting white-collar corruption cases.

Trump, in his tweets, has ignored that Mueller was appointed to head the investigation by Deputy Attorney General Rod Rosenstein, another Republican, although the president has also often targeted Rosenstein with acerbic comments.

The Washington Post said it found that 13 of 17 of Mueller's lawyers have previously registered to vote as Democrats. Nine of the 17 have made political contributions to Democrats, including six to Trump's 2016 opponent, Democrat Hillary Clinton.

Trump's latest complaints about the Mueller probe come as his lawyers negotiate with Mueller's team over whether the president will answer prosecutors' questions and under what terms.

Mueller has threatened to subpoena Trump to testify under oath before a grand jury, but a new Trump lawyer, former New York Mayor Rudy Giuliani, claimed Sunday that Trump can ignore a subpoena and might invoke his constitutional right against self-incrimination if he is forced to answer questions.

The question of whether the president can be forced to testify could ultimately be decided by the U.S. Supreme Court.