After decades of planning, the rebuilding of America’s busiest train station, Pennsylvania Station in New York City, will begin in about two years, federal transportation officials said on Wednesday.

Sean P. Duffy, the federal transportation secretary, and Andy Byford, the Amtrak executive whom the Trump administration recently put in charge of the project, planned to lay out that ambitious goal at a news conference on Wednesday afternoon, transportation officials said.

After taking control of the project this spring, Amtrak intends to partner with a private developer to renovate the dingy station, which sits beneath Madison Square Garden in Midtown Manhattan, on an accelerated schedule, the officials said. Under the new timeline, construction would begin by the end of 2027, they said.

But it was not clear how much the long-overdue overhaul would cost or who would pay for it. Amtrak owns the station, but its primary users are NJ Transit and New York’s Metropolitan Transportation Authority.

Earlier on Wednesday, Mr. Duffy announced that the Trump administration would take control of Union Station in Washington, D.C. That station, the second busiest on Amtrak’s national network, is owned by the U.S. Department of Transportation and controlled by Amtrak.

Still, Mr. Duffy told Fox Business in an interview on Wednesday that the administration was going to take the station back. “We’re going to drive out the homelessness, we’re going to drive out the crime,” he said.