The US Senate unanimously passed the Pentagon's 2013 budget on Tuesday, despite a political impasse over debt reduction that could see huge cuts to military spending next year.

After months of negotiations, lawmakers voted 98-0 to approve the $631 billion National Defense Authorization Act for Fiscal Year 2013, which began on October 1.

The sweeping measure, passed after five days of debate and hundreds of amendments, would tighten sanctions on Iran, restrict the president's authorization in handling terrorism suspects, and prohibit the military detention of US nationals.

The bill must be reconciled with a version passed earlier this year in the House of Representatives before going to President Barack Obama's desk for his signature, though the White House has threatened a veto.

The two versions have major differences, but both Senate Armed Services Committee chairman Carl Levin and ranking Republican John McCain expressed confidence in reaching consensus in conference.

The administration "strongly objects" to sections of the bill that would, among other things, impose restrictions on the use of funds to transfer detainees held at the US Naval base at Guantanamo Bay, Cuba to foreign countries; and to the proposed trimming of civilian and contract workers.

"If the bill is presented to the president for approval in its current form, the president's senior advisers would recommend that the president veto the bill," the Office of Management and Budget said last week.

Obama had sought $614 billion, of which $89 billion would go to the war in Afghanistan.

But the Senate hiked the total figure by $17 billion, even as lawmakers and the president grapple with how to avoid hundreds of billions of dollars in automatic spending cuts that kick in next month if no deficit reduction deal is reached.

Tuesday's legislation saw more than 140 amendments added to the bill, including a ban on the US government detaining American citizens or US permanent residents without charge, and tough new economic sanctions on Iran aimed at stalling the Islamic republic's nuclear program.

It also includes an amendment requiring the administration to report to Congress on the US military options available for degrading Syrian President Bashar al-Assad's use of air power against his own people, although it does not expressly authorize the use of US military force and is not to be construed as a declaration of war against Syria.

The bill also provides a 1.7-percent pay raise for military personnel, strengthens the Pentagon's anti-sexual assault programs, and improves the care and management of wounded warriors, McCain said.

The bill also approves funding for the deployment of additional US forces to protect American embassies and diplomatic missions abroad -- a reaction to the September 11 attack on the consulate in Benghazi, Libya.

Four Americans including ambassador Christopher Stevens were killed in the attack by Islamist militants, and several investigations are under way to determine possible security lapses that contributed to the incident.

Tuesday's vote marked a rare moment of cooperation between the two parties. Democrats and Republicans are engaged in fierce negotiations on deficit reduction for the next 10 years; they have until the end of the month to forge a compromise, but as of Tuesday, the discussions seemed stalled.

"Our efforts demonstrate that when it comes to addressing the issues important to the men and women in uniform, the Senate can work together in a bipartisan manner," McCain said.