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President Donald Trump on Thursday morning escalated his complaints about the myriad of investigations he is facing, tweeting that there was "no reason" for the House Intelligence Committee to open a sweeping probe into whether his decision-making as president is motivated by financial gain.

So now Congressman Adam Schiff announces, after having found zero Russian Collusion, that he is going to be looking at every aspect of my life, both financial and personal, even though there is no reason to be doing so. Never happened before! Unlimited Presidential Harassment.... — Donald J. Trump (@realDonaldTrump) February 7, 2019

....The Dems and their committees are going “nuts.” The Republicans never did this to President Obama, there would be no time left to run government. I hear other committee heads will do the same thing. Even stealing people who work at White House! A continuation of Witch Hunt! — Donald J. Trump (@realDonaldTrump) February 7, 2019

Trump on Wednesday complained that House Intelligence Chairman Adam Schiff had "no basis to" expand his committee's Russia investigation, calling the California Democrat a "political hack."

“It’s just presidential harassment and it’s unfortunate and it really does hurt our country,” Trump told reporters of the new probe.

On Wednesday, Schiff announced that his committee would examine connections between the Trump campaign and Russia to determine whether any presidential decisions have been influenced by financial gain.

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Schiff said the probe would extend beyond Russian electoral interference and any possible links between the Trump campaign and Russian officials, and would examine the president's business and finances.

“The president’s actions and posture towards Russia during the campaign, transition and administration have only heightened fears of foreign financial or other leverage over President Trump and underscore the need to determine whether he or those in his administration have acted in service of foreign interests since taking office,” Schiff said in a statement, adding that his new probe would examine "whether any foreign actor has sought to compromise or holds leverage, financial or otherwise, over Donald Trump, his family, his business, or his associates."

The chairman responded to Trump calling him a "political hack," saying that it was understandable that congressional oversight "terrifies" the president.

"Several of his close associates are going to jail, others await trial, and criminal investigations continue," he added on Twitter. "We’re going to do our job and won’t be distracted or intimidated by threats or attacks."

The back-and-forth comes after Trump, in Nixon-esque fashion, attacked the ongoing investigations he faces during his State of the Union address.

"If there is going to be peace and legislation, there cannot be war and investigation," he said. "It just doesn't work that way!"

In his last State of the Union address, in 1974, President Richard Nixon called for an end to the Watergate probe. He would resign as a result of it later that year.

House Speaker Nancy Pelosi told reporters after a Democratic Caucus meeting on Wednesday that Trump's comment "was a threat."

"The president should not bring threats to the floor of the House," she said, adding, "He said he wasn’t going to cooperate unless we didn’t exercise our constitutional responsibility to oversight."

Senate Minority Leader Chuck Schumer told "CBS This Morning" on Wednesday that, to him, the line showed "that the president's scared."

"The bottom line is that we are as a country, we've always had Congress do oversight over the executive branch," Schumer said. "That's how the Founding Fathers set it up."

On CNN, Schumer compared Trump's position on congressional oversight of him to the recent partial government shutdown, which was the longest in U.S. history.

"And the president says if you investigate me I'm not going to make progress," he said. "That's already doing what he did with the shutdown. Holding the American people hostage. He's got something to hide. Because if he had nothing to hide, he'd just shrug his shoulders and let these investigations go forward. He's afraid of them."