(CNN) President Donald Trump is expected to select Deputy Secretary of State John Sullivan to replace Jon Huntsman as US Ambassador to Russia , according to a White House official.

CNN reported earlier this month that Huntsman has submitted his resignation letter to Trump and plans to move back home to Utah, according to a source familiar with his thinking.

Sullivan was a partner at Mayer Brown in Washington and co-chaired the law firm's national security practice before being nominated as former Secretary of State Rex Tillerson's deputy in April 2017. He previously served as chairman of the United States-Iraq Business Dialogue, a government advisory committee that dealt with US-Iraq economic relations.

Sullivan also held senior positions at the Justice, Defense and Commerce departments, including as deputy secretary and general counsel at Commerce, deputy general counsel at Defense and counselor to Assistant Attorney General J. Michael Luttig.

Trump told reporters on Tuesday that Sullivan "very well could be" the next US ambassador to Russia.

"He's somebody that's being put up and respected. To Russia? Yeah. Very respected," Trump told reporters in the Oval Office when asked if Sullivan is his pick to replace Huntsman.

"Well I know that (Secretary of State) Mike Pompeo likes him very much and he's very respected. He could very well be, yeah," Trump continued.

However, two sources tell CNN that Sullivan is well-liked at the State Department but is not inside Pompeo's inner circle.

Sullivan has often felt out of the loop and wanted a new post. Despite having little experience when it comes to Russia, Sullivan lobbied to get this job and Pompeo and national security adviser John Bolton ended up supporting him.

The sources said Pompeo and Bolton recognize that the US ambassador to Russia is a challenging role, but not one that holds a lot of significance in this administration.

Sullivan has defended the President's strategy in Russia, telling CNN's Christiane Amanpour last year before Trump's visit with Russian President Vladimir Putin that Trump wanted "to engage with" the Russian president.

"But our purpose is not to engage for purposes of surrendering our principles," Sullivan said. "The President's purpose is to engage with President Putin, so that we can discuss these important issues, whether it's Eastern Ukraine, Crimea, arms control, Syria. There are so many issues on which we need to engage with the Russians and have been."

Sullivan has very little experience when it comes to Russia. He led the US delegation that met with Russian officials last month in Geneva on arms control. He impressed State Department officials on that trip who called him a quick learn when it came to the highly technical nature of arms control.

During his first year as deputy, Sullivan also pushed back against "twisted" reports of deep unhappiness with Tillerson in the face of a redesign and looming cuts that could slash the country's oldest Cabinet agency by as much as 30%.

Huntsman's resignation is effective October 3 and there is some speculation that he is planning to run for governor of Utah, a role he previous served in from 2005 to 2009. However, a source close to Huntsman told CNN that decision is still up in the air, saying, "We shall see, it's been a long two years."

Special Representative to North Korea Steve Biegun, who was also on the short list for the Russia ambassador job, stayed on the DPRK portfolio given the escalating tension between the US and North Korea.