A sweeping $521 billion package that authorizes the military to expand operations against the Islamic State and provides billions for the upgrade of military equipment hit a snag on Tuesday over something that has nothing to do with the military.

Tucked inside the bill’s more than 1,600 pages is language creating six national parks, expanding nine others and establishing a bipartisan commission to explore building a national women’s history museum.

It would even settle a long-simmering dispute in the District of Columbia by redesignating the downtown Pershing Park as a national World War I memorial while leaving a small white structure on the Mall dedicated only to D.C.’s war veterans.

Sen. Carl Levin (D-Mich.), the retiring chairman of the Armed Services Committee who helped write the defense bill, said that negotiators agreed to include the massive expansion of federal land holdings in part because the military-themed legislation has passed for more than five decades, while parks and wilderness legislation has languished for more than five years.

But some GOP lawmakers warned Tuesday that they will use any available procedural tools to slow the bill’s eventual passage.

“A bill that defines the needs of our nation’s defense is hardly the proper place to trample on private property rights,” Sen. Tom Coburn (R-Okla.), a longtime opponent of what he views as excessive federal spending, wrote in a letter to GOP leaders that was released Tuesday.

Sen. Ted Cruz (R-Tex.) said that adding the land changes to the bill is “a disservice to members of the Armed Forces.”

Senior House and Senate aides still expect the defense bill to pass by next week. The White House has expressed general support for the process, but White House press secretary Josh Earnest said Monday that “we’re going to evaluate the whole package” before President Obama decides whether to sign the bill.

Members of both parties complained that the legislation is likely to sail across Capitol Hill with little debate and — under a special agreement — they will have no ability to offer amendments to the legislation. But they agreed that it would be an embarrassment not to approve a pay raise for troops and plans for the national defense before adjourning for the year.

“This isn’t a bill that should be the subject of the normal political give-and-take. It’s important for the national security,” said Sen. Angus King (I-Maine), who caucuses with Democrats and is a member of the Armed Services Committee.

“I would prefer amendments, but on the other hand we can’t do that now because we’re in a lame duck, where you just don’t have the time to really debate these matters,” said Sen. Orrin G. Hatch (R-Utah), the longest-serving GOP senator.

The bill’s passage will cap the congressional careers of Levin and Rep. Howard P. “Buck” McKeon (R-Calif.), who chairs the House Armed Services Committee. Both men are retiring next month.

They worked during the past several months on the legislation, which authorizes $63.7 billion for ongoing overseas military operations and allows the Pentagon to move forward with its initiative to train and equip moderate Syrian rebels, a central part of the White House’s plan for combating the Islamic State, the militant group that controls a vast expanse across Iraq and Syria. The legislation would allow the U.S. military to train, arm, and potentially provide salaries to the rebels through the end of 2016.

If passed, the Pentagon could also spend money building facilities for the training program, which is expected to take place in Saudi Arabia, Turkey and other Middle Eastern nations. But lawmakers, mindful of the risks of sending a U.S.-armed force into Syria’s chaotic civil war, are requiring the Pentagon to provide detailed reports about who is being trained and what weapons are provided.

The bill would empower the Obama administration to spend $1.3 billion on a new “counterterrorism partnership fund.” The program, which Obama unveiled in May, would seek to combat extremist groups, including affiliates of al-Qaeda, by strengthening foreign militaries rather than sending U.S. soldiers to fight overseas. The White House had wanted $5 billion for the fund, but the price tag was reduced significantly in part because officials last month asked for an increase in wartime funding to respond to the military gains the Islamic State has made in Iraq since June.

The bill would also authorize the Pentagon to train, arm, and pay Iraqi forces — not only army soldiers but members of the Kurdish peshmerga security force and tribal fighters whose support is needed to combat the Islamic State.

Lawmakers did limit the amount the U.S. military can spend on that initiative if it fails to secure funding contributions from other countries involved in the fight against the Islamic State.

The bill also would keep terrorism detainees at the U.S. facility at Guantanamo Bay, Cuba, for at least another year.

Sen. John McCain (R-Ariz.), who opposes keeping the detainees at the military base, said that when he assumes control of the Armed Services Committee next year, “We’ll take up the issue . . . and give it a lot of attention and debate and discussion.”

The legislation authorizes a 1 percent across-the-board pay raise for service members but freezes the pay of generals and other senior officers. It also adds more changes to how the military handles cases of sexual assault and rape by eliminating the “good soldier” defense for troops accused of assault and allowing victims to help determine whether their case should be tried in military or civilian court.

The new national parks include the Manhattan Project National Historical Park that would preserve historic sites and artifacts in New Mexico, Tennessee and Washington.

The legislation also sets aside about 22,000 acres for the Tule Springs Fossil Beds National Monument in southern Nevada, a longtime priority for outgoing Senate Majority Leader Harry M. Reid (D-Nev.).

Missy Ryan contributed to this report.