WASHINGTON — Senate leaders reached last-minute agreement this morning to avert a threatened Treasury default and reopen the government after a partial, 16-day shutdown, according to a Republican senator who also said congressional leaders would push for passage as soon as possible.

The Dow Jones industrial average soared on the news that the threat of default was easing, rising roughly 200 points by late morning.

“I understand they’ve come to an agreement but I’m going to let the leader announce that,” Sen. Kelly Ayotte, R-N.H., said as she walked into a meeting of Senate Republicans called to review details of the emerging deal struck by Senate Majority Leader Harry Reid and GOP Leader Mitch McConnell.

Officials said the proposal called for the Treasury to have authority to continue borrowing through Feb. 7, and the government would reopen through Jan. 15.

There was no official comment from the White House, although congressional officials said administration aides had been kept fully informed of the negotiations.

While the emerging deal could well meet resistance from conservatives in the Republican-controlled House, the Democratic Leader, Rep. Nancy Pelosi of California, has signaled she will support the plan and her rank and file is expected to vote for it in overwhelming numbers.

That raised the possibility that more Democrats than Republicans would back it, potentially causing additional problems for House Speaker John Boehner as he struggles to manage his tea party-heavy majority.

Ayotte said she understood the legislation would first receive a vote in the House, an arrangement that would speed its way through Congress to President Barack Obama’s desk.