US Attorney General William Barr testifies during a Senate Judiciary Committee hearing on Capitol Hill in Washington on the Mueller report. File picture: Andrew Harnik/AP

Washington - Whether or not US special counsel Robert S. Mueller III will testify before Congress about his Russia election meddling report will be left to Attorney General William P. Barr, President Donald Trump said Thursday.

The president appeared to contradict himself just days after a Sunday tweet that included this statement: "Bob Mueller should not testify." Trump wrote that day that the former FBI director testifying before Democratic-run House committees would amount to the opposition party trying to invent evidence of negative information about him.

"No redos for the Dems!" Trump wrote Sunday.

But by Thursday, the president had returned to his original position on the issue.

"I'm going to leave that up to our very great attorney general," Trump told reporters during another impromptu White House question-and-answer session following a health care event. "He'll make a decision on that."

Trump then again falsely stated that Mueller's report "fully exonerated" him. The report, in fact, states the special counsel was unable to clear the president on obstruction of justice.

"There was no crime," Trump said again. "It was a witch hunt."

Democrats in Congress strongly disagree, as their investigations of Trump's Russia connections and questions about obstruction of justice continue as relations between the two sides worsen.

For instance, Speaker Nancy Pelosi of California and House Judiciary Chairman Jerrold Nadler of New York say the actions of Trump and Barr - including claiming executive privilege to block Congress from seeing a completely unredacted version of Mueller's report - amounts to a "constitutional crisis."

"President Trump has taken a series of actions over his two years as president where he has genuinely pushed the boundaries, across a whole range of things: criticizing sitting federal court judges, the way he talks about the media, and now the way that he is challenging the power of Congress," Senate Judiciary member Chris Coons, D-Del., said Wednesday.

"He's done this previously, in terms of spending decisions, he's done it in other ways, in terms of the reach and scope of his executive orders," Coons told CNN.

A day after the GOP-controlled Senate Intelligence Committee issued a subpoena to his eldest son, Donald Trump Jr., to get additional testimony, the president said his son did nothing wrong.

"The Mueller report came out, that's the Bible," Trump said, contending it failed to implicate Donald Jr. in any crime.

In what became one part mini-press conference and another part one of his political rallies, the president addressed a range of topics.

Trump expressed confidence in national security adviser John Bolton amid several foreign policy crises - and noted he often has to "temper" his hawkish aide.

"John's very good. He has strong views on things, which is OK," Trump said. "I'm the one who tempers him, which is OK. I have John Bolton and I have people who are a little more dovish than him."

One of those crises is North Korea, which U.S. and South Korean intelligence officials say fired two missiles overnight. Trump called them "short-range missiles."

"Nobody's happy about it," he said, adding his relationship with Kim Jong Un "continues." But the president poured cold water on the notion the two countries are nearing a nuclear disarmament pact: "I don't think they're ready to negotiate."

Ahead of the early evening resumption of trade talks with China in Washington, Trump sounded hopeful even as his top negotiators have said Beijing is backing away from the pact that was emerging.

"I think it'll be a very strong day frankly," he said of the evening meeting. "It was their idea to come back."

He said Chinese President Xi Jinping just sent him a "beautiful letter" that indicated a desire to work together.

In the session's most Trumpian moment, the president again suggested his Justice Department should investigate a former Obama administration official.

"He should be prosecuted for that," Trump said of former Secretary of State John Kerry, referring to conversations the longtime Massachusetts Democratic senator has had with Iranian officials since Trump took office. "He violated the Logan Act."

Trump often makes such public pronouncements without the Justice Department launching investigations.

dpa