WASHINGTON -- Former Georgia U.S. Sen. Sam Nunn plans to introduce Exxon Mobil CEO Rex Tillerson and retired Gen. James Mattis at their respective Capitol Hill confirmation hearings this week, a notable gesture of support from a Democrat who backed Hillary Clinton in last year's presidential race.

Nunn will be on hand tomorrow morning to give his seal of approval to Tillerson as the Senate Foreign Relations Committee mulls his nomination for secretary of state, according to three sources.

He'll do the same for Mattis before the panel he led for eight years, Senate Armed Services, at 9:30 a.m. on Thursday, per two committee aides. There he'll be joined by former Secretary of Defense William Cohen.

The gestures amounts to an olive branch to president-elect Donald Trump three months after Nunn called the New York businessman "an apprentice in the nuclear arena."

"Mr. Trump seems not to care what he doesn't know, and he apparently listens to no one. His colossal ego and disdain for military leaders are far from comforting," Nunn wrote in an October op-ed in The Wall Street Journal.

Nunn has a dog in the fight when it comes to the national security arena. As co-founder and CEO of the Nuclear Threat Initiative, Nunn has focused his post-Senate career on paring down the world's use of nuclear weapons. In that role, he's advocated for increased cooperation with Russia, the world's other great nuclear power, and has also been critical of the Obama administration for its handling of certain matters with the Kremlin.

Tillerson has been a fierce backer of maintaining U.S.-Russia relations, a position that's prompted criticism from Democrats and many Republicans. Nunn and Tillerson served together on the board of trustees of the Washington, D.C.-based Center for Strategic and International Studies.

Meanwhile, Nunn got connected to Mattis through projects at Stanford University.

Nunn isn't the only Georgia Democrat testifying in the Senate tomorrow on a Trump Cabinet nominee. U.S. Rep. John Lewis will take the witness stand Wednesday as Jeff Sessions' confirmation hearing for attorney general stretches into its second day.

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