WASHINGTON — President Obama’s overhaul of the nation’s immigration system, which he announced in a prime-time speech to the nation last November, may remain under a cloud of legal uncertainty until months before he leaves office in 2017, legal experts and administration officials said Wednesday.

Officials from the Justice Department said in a statement that they would not ask the Supreme Court for permission to carry out the president’s immigration programs — which seek to provide work permits and deportation protection to millions of undocumented immigrants — while a fight over presidential authority plays out in the lower courts.

That legal battle may extend for a year or more, officials said, undermining any hope of putting the president’s plan into effect until right before the 2016 election.

“The timing is critical,” said Stephen H. Legomsky, a law professor at Washington University in St. Louis. “If the process drags on until the summer of 2016, then implementation becomes very difficult.”