President Trump disparaged Robert Mueller and top ex-officials as Washington prepares for testimony from the special counsel in charge of the investigation into Russian interference in the 2016 election.

The president repeated a dubious claim that Mueller's team engaged in "illegal" activity by deleting text messages exchanged between former FBI officials Peter Strzok and Lisa Page as he retweeted a flurry of tweets from conservative watchdog group Judicial Watch.

"This is one of the most horrible abuses of all. Those texts between gaga lovers would have told the whole story. Illegal deletion by Mueller. They gave us 'the insurance policy,'" Trump tweeted Saturday morning.

Strzok and Page were said to be involved in an affair as they sent each other text messages that displayed disdain for Trump while they were involved in the Hillary Clinton emails and Russia investigations. Strzok was fired from the FBI in August 2018 and Page resigned a couple months earlier.

Trump has been accusing Mueller of deleting their text messages since it was announced he would testify about his now-completed investigation. Mueller was slated to appear publicly before the House Judiciary and Intelligence Committees next week, but a deal was struck to push it back to July 24 and allow more members to ask him questions. Throughout the 22-month-long inquiry, Trump said he was being targeted by a partisan "witchhunt." Mueller's report, released by the Justice Department with redactions in April, shows his team was unable to establish criminal conspiracy between the Trump campaign and the Kremlin and declined to clear Trump of obstruction of justice.

Strzok and Page's text messages were uncovered by Justice Department Inspector General Michael Horowitz, who found them over the course of his investigation into the FBI's handling of the Clinton emails investigation. Their exchanges were scrutinized by lawmakers on Capitol Hill — primarily House Republicans — concerned with the appearance of bias on the part of the FBI staffers, but the inspector general determined in June 2018 that the Clinton emails inquiry was not swayed by improper motivations.

In a separate report in December, the watchdog found no evidence the text messages had been deleted. Instead, investigators blamed the FBI's automated application that wirelessly gathers and saves data to and from its mobile devices for difficulty obtaining all text messages.

Trump also attacked former FBI Deputy Director Andrew McCabe, who briefly led the bureau after Trump fired Director James Comey in May 2017.

"Andy McCabe is a major sleazebag. Among many other things, he took massive amounts of money from Crooked Hillary reps, for wife’s campaign, while Hillary was under 'investigation' by FBI!" Trump tweeted Saturday morning.

McCabe was fired from the FBI on March 16, 2018, after the Justice Department's Office of the Inspector General determined he misled investigators about the role he had in leaking information to the Wall Street Journal in October 2016 about the investigation into the Clinton Foundation. McCabe argued that his firing was an attempt to discredit the FBI and Mueller's investigation. In April 2018, it was revealed that the Justice Department inspector general had referred its findings to the U.S. attorney’s office in Washington for possible criminal charges.

McCabe supports the House beginning impeachment proceedings against Trump, which is notably a step further than his former boss, Comey, has gone. Comey warned in March that the country "would see this as a coup" and has pushed for pushing Trump out of office in the 2020 election.