A bipartisan budget deal announced in the US Congress last night, though modest in its spending cuts, would end three years of impasse and fiscal instability in Washington that culminated in October with a partial government shutdown.

While praised by the Republican leadership of the US House of Representatives, including Speaker John Boehner and Majority Leader Eric Cantor, the agreement faces a challenge from some House conservatives and will require support of the minority Democrats to pass.

The backing of President Barack Obama, who also hailed the agreement as "a good first step," should help round up votes of his fellow Democrats. He urged Congress to quickly pass it.

The accord was uncharacteristic for a politically polarised Congress that in recent years has waited until the absolute last moments to reach stop-gap agreements on the budget and on raising US borrowing limits to avert historic debt defaults.

Instead, a deal was reached before a non-binding Friday deadline and more than a month before the January 15 date when existing funds to run many federal programmes expire.

The House is likely to put the deal to a vote by Friday, before recessing for the year, and a Senate vote might come next week.

Among the details of the bill are $6 billion in cuts to federal workers' retirement benefits and $6 billion in cuts to military pensions. These and other new savings would replace some of the second round of automatic spending cuts, known as "sequestration," that were scheduled to begin in January.