Former New Jersey Gov. Chris Christie (R) said Tuesday he doesn’t believe President TrumpDonald John Trump2020 Democrats spar over socialism ahead of first debate Senate passes .5 billion border bill, setting up fight with House 'Teflon Don' avoids the scorn of the 'family values' GOP — again MORE should sit for an interview with special counsel Robert MuellerRobert (Bob) Swan MuellerTop Republican considered Mueller subpoena to box in Democrats Kamala Harris says her Justice Dept would have 'no choice' but to prosecute Trump for obstruction Dem committees win new powers to investigate Trump MORE as part of the Russia investigation. 

“Robert Mueller is not someone to be trifled with. And he’s not someone who takes lightly the words of anybody who he’s looking at,” Christie said. 

“I don’t think there’s been any credible allegations against the president of the United States. And I don’t think the president of the Untied States, unless there are credible allegations, which I don’t believe there are, should be sitting across from a special counsel,” Christie added.

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Mueller is leading a criminal probe into Russia's election meddling and possible collusion between the Trump campaign and Moscow. His investigation has thus far led to two guilty pleas and two indictments. 

Trump said last week he would be willing to speak with Mueller under oath. A White House lawyer, however, clarified that details of an interview with Mueller are still being worked out.

Trump, who has labeled Mueller’s investigation a “hoax” and a “witch hunt,” reportedly sought to fire the special counsel last year, but was stopped by a top aide.

Christie, a former federal prosecutor, said he believes the Trump administration has cooperated with Mueller’s investigation, adding that he hasn’t seen evidence of an obstruction of justice case against the president.

“The fact is that that’s a very high standard to meet. We've all gone through this before, and I don’t think we’ve met that high standard yet as to President Trump. But we’ve got to continue to watch it,” Christie said.

Christie, who joined ABC News this week as a regular contributor, was among the first major politicians to endorse Trump during the 2016 campaign.