Former Georgia U.S. Sen. Sam Nunn threw his support behind Rex Tillerson on Wednesday, telling senators that President-elect Donald Trump’s nominee for secretary of state is “well prepared to do what is essential for the security of our nation.”

The Democrat’s move is notable not only because it gives the former Exxon Mobil CEO a boost from across the aisle. It also amounts to an olive branch to Trump, whom Nunn slammed last year for being “an apprentice in the nuclear arena” with “no appetite for learning.”

Addressing Democrats’ biggest concern about Tillerson, Nunn told members of the Senate Foreign Relations Committee that the nominee’s past business with the Kremlin would be an asset.

“I know Rex Tillerson pretty well, and I am confident that he is well prepared to do what is essential for the security of our nation: to hold firm and tough where our national interests and our values demand it and to build on our common interests in working with other nations — including Russia — on practical, concrete steps that will make the American people safer and more secure,” said Nunn, who served four terms in the Senate.

Nunn has built his post-Senate career on promoting nuclear cooperation, including with other superpowers such as Russia, through his nonprofit, the Nuclear Threat Initiative. In recent years he’s grown critical of the Obama administration for its handling of certain matters with the Kremlin.

The former senator joined Texas’ two U.S. senators and former Defense Secretary Robert Gates to perform the ceremonial duty of introducing Tillerson at the beginning of his confirmation hearing on Capitol Hill.

Tillerson and Nunn served together on the board of trustees of the Washington-based Center for Strategic and International Studies.

Nunn is slated to return to the Senate on Thursday morning to introduce retired Gen. James Mattis at his confirmation hearing for secretary of defense before the Armed Services Committee, the panel Nunn led for eight years.

Meanwhile, Nunn’s daughter Michelle, a former U.S. Senate candidate who now leads the Georgia-based humanitarian group CARE USA, took to the op-ed pages of the Washington newspaper The Hill on Wednesday to also voice her support for Tillerson and Mattis.