Christie: Trump should not meet with Mueller

"I don't think the President of the United States -- unless there are credible allegations, which I don't believe there are -- should be sitting across from the special counsel. The presidency is different. I don't think they should do that," Christie, who served as a US attorney for New Jersey for six years prior to becoming governor, told ABC's "Good Morning America."

Mueller is interested in asking Trump about his dismissals of former FBI Director James Comey and former national security adviser Michael Flynn, two sources familiar with the matter told CNN last week.

"Robert Mueller is not someone to be trifled with," Christie said. "What I've said all along is that in an investigation like this, there's ... nothing you can do to make it shorter. There are lots of things you can do to make it longer."

Christie's comments were quickly criticized by Preet Bharara, an Obama-era US attorney for New York who was ousted from his role by Trump last March.

"Reminder that @GovChristie is a former U.S. Attorney. If he were in charge of such an investigation, there is no universe in which he would not seek a Trump interview," Bharara, who is now a CNN senior legal analyst, tweeted.