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President Donald Trump on Wednesday sparred with his top law enforcement official, Attorney General Jeff Sessions, slamming his "disgraceful" handling of an inquiry into Republican allegations of surveillance abuses by the FBI in the Russia probe.

“Why is A.G. Jeff Sessions asking the Inspector General to investigate potentially massive FISA abuse,” Trump tweeted Wednesday morning. “Will take forever, has no prosecutorial power and already late with reports on Comey etc. Isn’t the I.G. an Obama guy?”

“Why not use Justice Department lawyers? DISGRACEFUL!” Trump added.

The tirade referred to a decision Tuesday by Sessions to allow his agency’s inspector general to determine whether FBI officials broke any rules or laws in obtaining a warrant to monitor the communications of a Trump campaign associate beginning in October 2016, around the same time the FBI began looking at possible Russians efforts to interfere in the presidential election.

Several Republicans have been clamoring for an investigation into possible surveillance abuses by the FBI in the weeks since the House Intelligence Committee made public a controversial GOP memo that raised questions about the agency’s application for surveillance authority that was presented to the Federal Intelligence Surveillance Act (FISA) Court. That application granted the FBI the ability to conduct secret surveillance on Carter Page, an aide to Trump's presidential campaign.

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In a rare move, Sessions defended himself in a sharply worded statement in which he said he would continue to do his work “with integrity and honor” — as long as he stayed on the job.

“We have initiated the appropriate process that will ensure complaints against this Department will be fully and fairly acted upon if necessary,” Sessions said in a statement. “As long as I am the Attorney General, I will continue to discharge my duties with integrity and honor, and this Department will continue to do its work in a fair and impartial manner according to the law and Constitution.”

Sessions, who has become a frequent target of Trump's ire, had never in the past publicly refuted criticism from the president like he did on Wednesday.

Rep. Trey Gowdy, R-S.C., the chairman of the powerful House Oversight Committee and a member of the House Intelligence Committee, defended the Justice Department inspector general, Michael Horowitz, as "fair" and "fact centric" after Trump’s Twitter attack.

"I have had a number of interactions with Inspector General Horowitz, including as recently as earlier this month. He has been fair, fact centric, and appropriately confidential with his work," Gowdy said in a statement. "He was confirmed by the U.S. Senate without a single dissent. I have complete confidence in him and hope he is given the time, the resources and the independence to complete his work."

Rep. Pete King, R-N.Y., a Trump supporter, warned the president to back off from his criticism of Sessions.

"I wouldn’t do that," King told Fox News. "I would not publicly criticize Jeff Sessions because I know how loyal he is to the president."

But Liberty University President Jerry Falwell Jr., one of the nation's most prominent evangelical Christian leaders and a Trump supporter, called Sessions a "coward."

"I couldn’t agree more. @USAGSessions must be part of the Bush/Romney/McCain Republican Establishment," Falwell tweeted. "He probably supported @realDonaldTrump early in campaign to hide who he really is. Or he could just be a coward."

Trump’s tweet Wednesday was just the latest critique the president has levied against Sessions, who during the presidential campaign was the first sitting U.S. senator to endorse the first-time candidate.

But following Session’s decision last March to recuse himself from any federal probe of Russian meddling in the presidential election — which helped to trigger the appointment of special counsel Robert Mueller — Trump has repeatedly and publicly attacked him.