US House of Representives Speaker-elect Paul Ryan (left) salutes the members of the House as he stands with outgoing speaker John Boehner after his election on Capitol Hill in Washington.

AFP/Washington

The US Senate passed a bipartisan, two-year budget deal early Friday that boosts federal spending by $80bn, reduces a government shutdown threat and raises the debt ceiling through the end of Barack Obama's presidency.

The bill passed the House of Representatives on Wednesday and now goes to Obama for the formalities of his signature, although the political fallout looks set to linger on.

The measure, which passed 64 votes to 35 late into the night, provides lawmakers with some fiscal breathing room through the 2016 presidential election after years of bruising spending fights.

The plan suspends the statutory federal borrowing cap until mid-March 2017 and averts a damaging default.

It provides for a $50bn spending increase in fiscal 2016 - split about equally between defence and domestic programmes - and $30bn in fiscal 2017.

It also adds $31bn into an emergency war fund for the Pentagon, offset by tweaks to entitlement programs including Social Security.

The deal is the result of weeks of secret negotiations between the White House and Republican then-speaker John Boehner, who sought to clear the decks of any fiscal crises before his successor took the gavel.

Boehner stepped down on Thursday, when congressman Paul Ryan was elected as the new speaker of the House, and the bill marked Boehner's final legislative achievement.

There was a sense of urgency to the Senate vote, which occurred hours before sunrise on Friday.

The Republican-controlled Congress must raise the federal borrowing limit by November 3, or risk Washington ending up in default.

Senate Minority Leader Harry Reid praised lawmakers for coming together to pass the bill, which he said "will help prevent a government shutdown and avoid a disastrous default on our nation's obligations."

'Unholy alliance' 

Overall, the new budget would set 2016 discretionary spending at $1.067tn, of which about half is for defence. The figure would rise slightly in 2017, to $1.071tn.

Congressional appropriators will need to decide how the funds will be divided among the vast slate of federal programs by December 11, when a stopgap spending measure expires.

But several conservatives, including a number of candidates vying for the Republican presidential nomination, have blasted the deal as fiscal recklessness.

Critics say it marks a sell-out to the Obama administration because it busts through congressionally mandated spending caps and extends borrowing authority, while doing little to pare down the nation's $18tn deficit.

"Republican majorities have just given President Obama a diamond-encrusted, glow-in-the-dark AmEx card," Senator Ted Cruz, who is running for president, fumed late on Thursday.

Senator Rand Paul, a rival GOP presidential contender, accused fellow Republicans and Democrats of having "come together in an unholy alliance to explode the debt."

"The left gets more welfare, the right gets more military contracts, and the taxpayer is stuck with the bill," Paul said.

Republican and Democratic lawmakers fought several battles over borrowings between 2011 and 2014 that roiled financial markets, caused an unprecedented downgrade of the country's triple-A debt rating by Standard & Poor's, and forced a partial government shutdown for 16 days in 2013.