The Senate is heading toward passage of a defense policy bill that would authorize $602 billion in military spending, prohibit the closing of the detention facility at Guantanamo Bay, Cuba, and require young women to register for a potential draft.

In a rare Friday session, the Senate voted 68-23 to proceed with the National Defense Authorization Act.

A vote on the legislation had been scheduled for earlier this week as lawmakers sought to resolve differences over potential amendments to the bill. Among them are measures that would allow Afghan civilians who assisted the American-led coalition to resettle in the United States, alter the military justice system to curb sexual assaults, and prohibit the indefinite detention of U.S. citizens.

The White House has threatened to veto the bill, objecting to the Guantanamo provision and others — including one that would limit the size of the president's National Security Council staff.

Even as progress in the Senate loomed, a prominent conservative group on Friday called for the legislation to be rejected over the female draft registration requirement and a lack of funding to modernize the military after 15 years of non-stop demands.

"Regardless of whatever merits the bill may have, it deserves to be defeated because lawmakers should not force young women into military services through the Selective Service," Heritage vice president Dan Holler said in an emailed statement.

A dispute that erupted late Thursday underscored divisions among Republicans, many of whom have called for the bill to be passed urgently.

A bipartisan group of senators is pushing to extend and expand a program that gives visas to Afghans who defied the Taliban and worked for the coalition as interpreters, firefighters and construction laborers. Without the option to leave, they and their families risk being harmed or killed by militants, the top American commander in Afghanistan has warned.

Despite broad backing, an amendment to keep the so-called special immigrant visa program from expiring bogged down after Sen. Mike Lee, R-Utah, objected to a vote being held.

Lee, who said he supports the Afghan visa program, demanded that senators also agree to a vote on his amendment that prevents the government from detaining indefinitely U.S. citizens apprehended on American soil for being suspected of supporting a terrorist group.

But Sen. Lindsey Graham, R-S.C., objected to a vote on Lee's amendment, leading to a stalemate. Graham said Lee's amendment could lead to terrorists being treated as criminals instead of enemy combatants.

The chairman of the Senate Armed Services Committee, Republican John McCain of Arizona, on Friday lamented the objections, saying that's not the way the Senate is supposed to operate.

"I have reached a level of frustration that I would even consider changing the rules of the Senate (so) that one individual out of 100 can't bring everything to a screeching halt," McCain said.

Due to the Senate's procedural rules, McCain said he was forced to object to an amendment by Sen. Kirsten Gillibrand, D-N.Y., that would make a major change in how the military handles allegations of sexual misconduct.

Her measure would strip senior military officers of their authority to decide whether sex crimes and other serious offenses go to trial. That responsibility would be given instead to independent military trial counsels. Proponents of Gillibrand's amendment say a seismic change is needed to end sexual assaults in the ranks.

But the Pentagon has objected. U.S. military officials said curbing a commander's power to punish or pardon service members will send a message there is a lack of faith in the officer corps. They've also argued that removing the prosecution decision from the chain of command will mean fewer victims of sexual assault get justice.

Sen. Jerry Moran, R-Kansas, is seeking a vote on his amendment that would bar the Defense Department from spending money on the design, construction or modification of facilities in the United States to house Guantanamo detainees. Moran's measure is spurred by the possibility of detainees being moved to the Army prison at Fort Leavenworth, Kansas.