The National Park Service will cope with budget cuts by requiring unpaid leave for the police who guard Washington's monuments, and Smithsonian museums will close some art galleries on a rotating basis, agency heads said Tuesday at a congressional hearing.

"We cannot keep every gallery or exhibition in every museum open daily without sufficient security," Smithsonian Institution Secretary G. Wayne Clough told the House Committee on Oversight and Government Reform.

Clough and the head of the National Park Service spoke about how they were reducing costs after across-the-board federal budget cuts went into effect in March. The Smithsonian had implemented a hiring freeze in anticipation of losing $41 million in funding.

The Smithsonian's art gallery guards are hired under contract to supplement the permanent museum security staff, according to Smithsonian spokeswoman Linda St. Thomas. When those gallery security contracts are reduced after May 1, museum visitors may find some galleries temporarily closed.

Budget cuts could also delay construction, fundraising and hiring for the new National Museum of African American History and Culture, which is scheduled to open in November 2015. Clough said other Smithsonian museums might have to cancel or postpone exhibitions, delay repairs to facilities and "significantly" reduce maintenance plans.

In the long term, Clough said the Smithsonian Institution still needed to figure out how it would cope with permanent reductions.

"Have we come to a point in time where offering the Smithsonian free to everyone is something we can afford?" Rep. Jackie Speier, D-Calif., asked during the committee's questioning.

"We've talked a lot about that," Clough said. "The American people paid for the buildings, they paid for the collections, and I don't think they should have to pay a third time to get into the museum."

Jonathan Jarvis, director of the U.S. National Park Service, testified that his agency will soon require up to 14 days of unpaid leave for its 767 U.S. Park Police employees, including those who guard Washington's monuments and are responsible for public safety at large events on the National Mall.

Those furlough days will be scheduled between April 21 and the end of the fiscal year on Sept. 30, according to Park Service spokesman Jeffrey Olson.

The agency also implemented a hiring freeze on permanent staff positions and will have about 1,000 fewer seasonal employees this year.

"It was a very, very difficult law to implement halfway though the year," Jarvis said as House committee members questioned him about how the National Park Service had prepared for the impact of the cuts.