— Senate Minority Leader Chuck Schumer said on Sunday that President Donald Trump should not voice his concerns about the impeachment hearings on Twitter but instead should appear before Congress to testify.

The New York Democrat's comments follow the first public hearings in the House impeachment inquiry into the President and Ukraine. Trump has continuously tweeted arguments in his own defense and lashed out at Democrats about the probe, calling it a "witch hunt." A number of former and current Trump administration officials have defied subpoenas seeking testimony before the House Intelligence Committee, and in some cases the White House has instructed administration officials to assert executive privilege.

"I think the hearings have brought up many many troubling allegations. And this morning (House) Speaker (Nancy) Pelosi invited President Trump to come testify, and I think her invitation is correct. If Donald Trump doesn't agree with what he's hearing, doesn't like what he's hearing, he shouldn't tweet. He should come to the committee and testify under oath and he should allow all those around him to come to the committee and testify under oath," Schumer said at an unrelated news conference in New York City.

He continued: "When Donald Trump refuses to come to the committee, now that Speaker Pelosi has invited him, when he doesn't let all the people around him come before the committee, you've got to ask the question: What is he hiding? What is he afraid to confront what these people have said?"

When CNN reached out to Schumer's office about the comment, his aide explained that Schumer's remark was cemented in Pelosi's comments during a CBS News interview that Trump "has every opportunity to present his case" before impeachment investigators or in writing.

In a letter to Pelosi in October, the White House called the impeachment inquiry "illegitimate" and "unconstitutional," and said that it would not participate in the investigation.

On Friday, Trump attacked former Ambassador Marie Yovanovitch in a pair of tweets as she gave her testimony, saying everywhere she went "turned bad." Some lawmakers have called Trumps tweets about Yovanovitch witness intimidation.

When asked if witness intimidation charges would be added to articles of impeachment, Schumer said he did not know if Trump's tweets meet a legal standard.

"That's a very serious legal charge. I didn't like what the President did ... but I don't know if it meets a legal standard. I leave that to the lawyers," he said.

Pelosi called Trump's tweets about Yovanovitch "totally wrong and inappropriate."

"I haven't had a lot of time to pay attention to the President's tweets and the legal implications of them," the California Democrat said. "I just think that was totally wrong and inappropriate and typical of the President."