The Senate on Tuesday reaffirmed a ban against torturing detainees and moved ahead on a more than $600 billion defense policy bill that is entangled in a broader fight in Congress about caps on Pentagon and non-military spending.

The Senate overwhelmingly voted 78 to 21 to approve an amendment that bolsters current law and makes the U.S. Army Field Manual on interrogations the standard for all interrogations conducted by the U.S. government. It also gives the International Committee of the Red Cross access to every detainee held by the U.S.

The vote comes just months after the Senate intelligence committee released findings of a classified investigation that said the CIA's brutal interrogations of al-Qaida detainees after 9/11 were harsher than previously thought.

Democratic Sen. Dianne Feinstein of California, who introduced the amendment with Republican Sen. John McCain of Arizona, said it was important because the presidential executive order banning torture could one day be lifted by a future president.

"I ask my colleagues to support this amendment and by doing so we can recommit ourselves to the fundamental precept that the U.S. does not torture — without exception and without equivocation — and ensure that the mistakes of our past are never again repeated in the future," she said.

California Rep. Adam Schiff, the ranking Democrat on the House Permanent Select Committee on Intelligence, said he would do all he can to support the measure in the House.

"By ensuring that the Army Field Manual exclusively applies to all U.S. government interrogations and by mandating access to detainees by the International Committee of the Red Cross, we will make sure America lives up to its highest ideals," Schiff said.

Christopher Anders, senior legislative counsel for the American Civil Liberties Union, said the measure would permanently ban the CIA from using any tactics that the military cannot use and will prohibit the CIA from hiding detainees from the Red Cross.

"If enacted, the amendment will be a historic step towards helping ensure that the federal government never again uses torture and abuse," Anders said.

After voting on amendments, the Senate voted 83 to 15 to move ahead on the defense policy bill that would authorize spending for the Defense Department and related programs. Still to come is action on defense appropriations bills that actually allow money to be spent.

President Barack Obama has threatened to veto any spending bill that locks in the automatic caps that Congress imposed a few years ago to address government deficits. He says he won't accept fixes to the defense budgeting problem that don't also address money spent on domestic programs. Democrats say they will block the Senate from even voting on a defense appropriations bill.

Republicans accuse the Democrats of blocking money used to support the U.S. armed forces.

The idea that Democrats would threaten to filibuster the defense appropriations bill, "which is the bill that actually pays the salaries of our troops is just unconscionable," said Sen. John Cornyn, R-Texas. "So we would ask them to reconsider and to work with us to continue passing bipartisan legislation and doing the people's work, and not to engage in this frivolous exercise known as 'Filibuster Summer.'"

Democrats say they want Republicans to sit down with them and discuss ways to unlock spending caps for both defense and non-defense spending, especially in light of Obama's veto threat.

"If you're driving down the road and you see a sign says 'Road closed ahead,' most people pay attention and they find another route," said Sen. Dick Durbin, D-Illinois. "Republicans have seen a sign from the White House that says 'This budget route is closed ahead' — the president is going to veto this appropriations bill."

In other business, the Senate voted down an amendment for the U.S. to bypass Baghdad and send arms directly to Iraqi Kurdish fighters battling Islamic State militants. The amendment would have temporarily given defense equipment to the Kurdish Regional Government in northern Iraq, which has complained about delays in getting arms through Baghdad.

The Senate also rejected a measure that would leave military commanders out of the decision to prosecute sexual assault cases in the military. Democratic Sen. Kirsten Gillibrand of New York, chief sponsor of the Military Justice Improvement Act, argued that recent reforms have not been enough to improve the way that sexual assault cases are handled by the military. She called on Congress to overhaul the military justice system to end retaliation against victims of sexual assault in the military.