How do you slash, cut, restructure and even dismantle parts of the federal government?

If you’re President-elect Donald J. Trump, you turn to two wealthy entrepreneurs: the spaceship-inventing, electric-car-building owner of a social media platform and a moneymaking former pharmaceutical executive who was once one of your presidential rivals.

Mr. Trump said on Tuesday that Elon Musk and Vivek Ramaswamy will lead what he called the Department of Government Efficiency. It will be, he said, “the Manhattan Project” of this era, driving “drastic change” throughout the government with major cuts and new efficiencies in bloated agencies in the federal bureaucracy by July 4, 2026.

“A smaller Government, with more efficiency and less bureaucracy, will be the perfect gift to America on the 250th Anniversary of The Declaration of Independence,” Mr. Trump wrote in a statement. “I am confident they will succeed!”

The statement left unanswered all kinds of major questions about an initiative that is uncertain in seriousness but potentially vast in scope. For starters, the president-elect did not address the fact that no such department exists. And he did not elaborate on whether his two rich supporters would hire a staff for the new department, which he said is aimed in part at reducing the federal work force.

Mr. Musk, who became one of Mr. Trump’s biggest campaign contributors, said before the election that he would help the president-elect cut $2 trillion from the federal budget. But he did not explain in any detail how that would be accomplished or what parts of the government would be slashed.

“This will send shockwaves through the system, and anyone involved in Government waste, which is a lot of people!” Mr. Musk said in the statement.

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