Donald Trump Continues Thank-You Tour, Will Formally Announce James Mattis as Secretary of Defense Pick President-elect expected to join retired Gen. James Mattis at event.

 -- Donald Trump is hitting the road again for the second leg of his post-election thank-you tour, stopping in Fayetteville, North Carolina, tonight to express gratitude to his supporters who helped him get to the White House.

After a busy day of meetings at Trump Tower in New York, the president-elect is scheduled to fly out later today for the 7 p.m. ET rally.

He will be joined there by retired Marine Gen. James Mattis, whom Trump will formally announce tonight as his pick for secretary of defense, transition team communications director Jason Miller said this morning.

Mattis retired in 2013 after a 41-year career in the Marine Corps. He emerged as a front-runner for the Cabinet position of defense secretary after Trump met with him in Bedminster, New Jersey, last month. After their meeting, Trump said he was impressed by Mattis.

Trump launched his thank-you tour last week in Ohio with a rally in Cincinnati, where he said he "had a lot of fun fighting" Hillary Clinton.

He teased the announcement of Mattis to attendees, saying, "We are going to appoint 'Mad Dog' Mattis as our secretary of defense. But we're not announcing it until Monday, so don't tell anybody. Mad Dog, he's great. He is great," Trump said, using one of Mattis' nicknames.

Trump will travel later this week to Iowa and Michigan, two other battleground states that were vital to his win.

ABC News' Katherine Faulders contributed to this report.