President Donald Trump on Wednesday called on Attorney General Jeff Sessions to end special counsel Robert Mueller's Russia investigation, one of the most direct demands he has made of the Justice Department to stop the probe since it began.

"Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further. Bob Mueller is totally conflicted, and his 17 Angry Democrats that are doing his dirty work are a disgrace to USA!" the president said in a morning tweet.

Sessions recused himself from overseeing the investigation into Russian interference in the 2016 U.S. presidential election over conflict of interest concerns, because he had served as a surrogate for Trump's campaign.

Sessions, during a speech in Arkansas about violent crime later Wednesday, appeared to joke about the tweet, musing about how Trump can send orders out “pretty quick.”

“The day I was sworn in as Attorney General, President Trump sent me a clear order. He can send out orders pretty quick. And, you know, he’s serious about it and we salute. But this is one I really embraced, I got to tell you. He told me ‘reduce crime in America,’” Sessions said.

Trump has repeatedly slammed Mueller's probe investigating Russian interference in the 2016 U.S. presidential election, including any potential communication with the Trump campaign.

The president has also repeatedly attacked Sessions for recusing himself from the Russian investigation. This past June, he directly criticized Sessions in a tweet for removing himself from overseeing Mueller, saying if he had known the attorney general would do that, he would have appointed someone else to that position instead.

“The Russian Witch Hunt Hoax continues, all because Jeff Sessions didn’t tell me he was going to recuse himself,” Trump tweeted. “I would have quickly picked someone else. So much time and money wasted, so many lives ruined … and Sessions knew better than most that there was No Collusion!”

Trump reportedly tried to get Sessions to maintain control of the probe shortly after he informed the president about his decision to step aside last year, but the attorney general rebuffed the request. The New York Times reported that the request is also being investigated by Mueller.

After Sessions stepped aside, Deputy Attorney General Rod Rosenstein, who appointed Mueller, assumed control of the probe. Rosenstein, who has also drawn the president's ire, has told colleagues that he may get fired and is at peace with the possibility.

A bipartisan congressional effort to pass legislation to protect Mueller's position appeared to hit a dead end earlier this year when GOP leadership in both chambers said they would not bring the measure up for a full vote. House Speaker Paul Ryan, R-Wis., said at the time that he believed such a bill was "unnecessary" because, "based on the kinds of conversations we have had," he believed that the president would not take steps to remove the special counsel.

"It would not be in the president's interest to do such a thing and I think he knows that," Ryan told reporters in April, shortly after the president suggested that he had not ruled out firing Mueller, and White House press secretary Sarah Sanders confirmed that Trump "certainly believes he has the power to do so."

At a press briefing Wednesday Sanders told reporters that Trump’s tweet was “not an order,” but rather “the president’s opinion.” She added that “the president isn’t obstructing, he’s fighting back” by “stating his opinion.”

Trump’s personal attorney Rudy Giuliani also told NBC News that the president "the president was expressing his opinion on his favored medium for asserting his First Amendment right of free speech."

“He said should, not must, and no Presidential order was issued or will be,” Giuliani added, referencing Trump’s tweet.

Ryan spokeswoman AshLee Strong, meanwhile, said Wednesday that the House speaker continues to back Mueller's probe. "The speaker has said many times the investigation should continue to its conclusion. I’ll refer you to those comments. His position has not changed," she said in a statement that did not address the president's comments directly.

Lawmakers on Capitol Hill reacted swiftly to the president's tweet, with top Democrats calling the statement evidence that the president is trying to obstruct justice, while some Republicans argued the president was merely voicing his opposition to the probe, and was well within his rights to do so.

"25 Russians indicted. 5 guilty pleas. Mr. President, what you call a stain, we call a justice system standing strong for our democracy. Your fear of this investigation will not bring it to an end," Rep. Joe Kennedy III, D-Mass., said in a tweet on Wednesday, referring to the status of the Mueller investigation.

Sen. Richard Blumenthal, D-Conn., a member of the Senate Judiciary Committee, said Trump's statements harshly critical of law enforcement could be considered evidence of obstruction of justice, another area being investigated by Mueller.

"If it isn’t obstruction of justice itself, it is evidence of intent to obstruct justice," Blumenthal said. "These kinds of threats are no accident, they reflect a state of mind to obstruct justice. The threats and bullying from the President of the United States against a law enforcement officer constitute evidence of obstruction of justice."

Rep. Adam Schiff, D-Calif, also said that the president's tweet was evidence of obstruction of justice. "The President of the United States just called on his Attorney General to put an end to an investigation in which the President, his family and campaign may be implicated," he tweeted. "This is an attempt to obstruct justice hiding in plain sight. America must never accept it."

But Senate Minority Leader Chuck Schumer, D-N.Y., said the president's call on Sessions to end the probe is "just another attempt to make the American people look at his latest shiny object."

Meanwhile, Sen. John Kennedy, R-La., defended Sessions, saying the attorney general had had no choice but to recuse himself. He also said that he supports Mueller's probe no matter the conclusion, but did not blame the president for lashing out at the probe because the longer the investigation continues the more rumor and spin it creates.

"That’s why I’ve strongly suggested to Mr. Mueller that he try to bring this investigation to a conclusion as quickly as he can without sacrificing thoroughness. And report the facts to the American people," Kennedy said. "And I think the president’s tweet is just one more symbol of what happens when this stuff just keeps dragging on, and dragging on, and dragging on."

And Sen. Marco Rubio, R-Fla., a member of the Senate Intelligence Committee, said that he believes the Mueller investigation will conclude and the truth will emerge.

"The Attorney General is going to do what he's going to do. Mueller is going to finish his investigation," Rubio said. "The truth is all going to come out. And that's the best thing that can happen for the president and for the country."