Aides to both Romney and Christie confirmed the appearance on Saturday, as Christie huddled with fellow state leaders at the National Governors Association annual meeting in Washington, held at the JW Marriott hotel.
Thursday's event will be focused on raising funds for the Republican Governors Association, which is chaired this year by Christie. Romney will make remarks at an evening dinner and then huddle with Christie and donors.
In an interview with The Washington Post in January, Romney, a former RGA chairman, said Christie's chairmanship is an important post for any politician looking to make a mark on the national stage. "It's part of what Karl Rove used to call the invisible primary," Romney said. "It's a chance to be seen and travel the country."
On Saturday, Christie kept a low profile at the NGA forum, spending much of the morning sitting quietly near the podium, with his black-rimmed glasses hanging on his nose, taking notes as other governors spoke.
Christie and his wife, Mary Pat, traveled to Washington on Friday by train and attended several RGA events in Washington on Friday afternoon. They will return to New Jersey on Sunday morning. They will not, however, visit the White House with other governors on Sunday. Christie also did not meet with reporters, and he declined to take questions about last year's lane closures on the George Washington Bridge, an apparent act of political retribution against the Democratic mayor of Fort Lee, N.J.
Next week, before heading to Massachusetts, Christie will unveil his budget and hold a town-hall meeting, his second of the year following a session last week in Middletown, N.J., an area hit hard by Hurricane Sandy in 2012.
Romney associates said the former governor is looking forward to the gathering, which will be close to his home and a boost for Christie.
"They've stayed close since the election," said Ron Kaufman, a former Romney adviser who will attend the private fundraiser. "Governor Christie was very good to Governor Romney during the presidential election, and Governor Romney was one of the first contributors to Governor Christie's reelection campaign. This will be a time for friends to come together and support all Republican governors."