Republican Chris Christie, former governor of New Jersey and Donald Trump rival for the 2016 GOP presidential nomination, told CNBC on Monday he wants to help his "friend" the president, but he's content to do it from afar.

"I'm not one of these people who's desperate for a job. I think I turned down seven of them down," Christie said in a "Squawk Box" interview. "I'm not desperate for a title. I'm not looking to run to Washington, D.C. What I'm looking to do is to make the country better and to help my friend."

Among the jobs that Christie said he declined in the Trump administration included Labor secretary, Homeland Security secretary, special assistant to the president, ambassador to Rome and ambassador to the Vatican.

"He hasn't offered me anything that I really wanted to do," said Christie, author of "Let Me Finish: Trump, the Kushners, Bannon, New Jersey, and the Power of In-Your-Face Politics."

"If there's something I really want to do and I think I bring real value to him and the country I'll step up and do it," he added. "I can certainly help him from where I am. And it's much better for my family if I stay where I am."

In his book, Christie describes the discussions around his support of Trump after dropping out of the 2016 race. The former governor writes that he said,at the time that his endorsement was not conditional, but he was only interested in the vice president or attorney general jobs, which respectively went to then-Indiana Gov. Mike Pence and then-Sen. Jeff Sessions.

After a tumultuous relationship with Trump over the investigation into Russia's alleged influence in the 2016 election by special counsel Robert Mueller, Trump forced out Sessions last November. William Barr was sworn in as Sessions' replacement last month. The 68-year-old Barr served as George H.W. Bush's attorney general.

Christie told CNBC he advised the president after the firing of James Comey as FBI director in May 2017, a move that eventually led to Mueller's appointment. Christie, himself a former U.S. attorney, suggested a potential replacement for Comey – and the name turned out to be Trump's eventual choice.

"When he fired Jim Comey, we talked extensively about who should replace him. And I brought the name Chris Wray to him," Christie said. "And he became convinced that Chris was the right guy, and has been supportive of Chris as he's moved to really change the FBI."

Wray, who was Christie's attorney in the Bridgegate scandal and served as assistant attorney general for the Criminal Division under George W. Bush, was sworn in as FBI director in August 2017.

Since his book came out, Christie told CNBC, he has spoken to Trump. The president said, "'You're nice to me,'" recalled Christie, who described how best to communicate with Trump. "Sometimes that means telling him something he doesn't want to hear. Sometimes he takes it very well and listens, and takes it all in. Sometimes he tells me, 'Didn't I beat you? Why do I have to listen to you?' It depends on the day."

"That's the ABCs of him, and that's what you've got to get used to if you've been his friend for 17 years. Nothing new," concluded Christie.