“He will, I think, grasp the challenge of moving the transportation sector toward a net-zero emissions profile by 2050,” Mr. Podesta added.

Mr. Buttigieg now stands as the first major member of Mr. Biden’s domestic climate change team, which the president-elect had hoped to roll out in its entirety this week.

Several sources close to the presidential transition said Mr. Biden had selected Gina McCarthy, who led the Environmental Protection Agency in the Obama administration, to lead the White House office of climate policy, and Jennifer Granholm, the former governor of Michigan, as the energy secretary.

But the nomination of an E.P.A. administrator has been held up with concerns over racial equity.

Mr. Biden’s first choice to head the agency was Mary D. Nichols, California’s top climate change regulator. But she came under fire from liberal activists who contended that Ms. Nichols did not do enough in her state to address racial disparities in environmental policy.

That has set off a scramble to find a candidate of color to lead the agency: last-minute possibilities include Richard L. Revesz, an Argentina-born law professor and former dean of N.Y.U. School of Law; Michael S. Regan, who currently serves as head of the North Carolina Department of Environmental Quality and is Black; and Eric Garcetti, the mayor of Los Angeles, who is of Mexican descent.

If confirmed, Mr. Buttigieg would be not only the first openly L.G.B.T.Q. person to hold a cabinet-level position in the Biden administration, but the first in any cabinet, according to the Human Rights Campaign, an advocacy group that last month pressed Mr. Biden to appoint L.G.B.T.Q. people to his cabinet.

“His voice as a champion for the L.G.B.T.Q. community in the cabinet room will help President-elect Biden build back our nation better, stronger and more equal than before,” said Alphonso David, the president of the Human Rights Campaign.