WASHINGTON — Montana’s Malmstrom Air Force Base could begin to lose part of its nuclear missile stockpile as soon as next month.

Rep. Denny Rehberg, R-Mont., said Wednesday that the Pentagon has confirmed it will remove 50 Minuteman III weapons, known as intercontinental ballistic missiles, from the Montana base. That is a quarter of the base’s total nuclear missile fleet.

The Pentagon last year said it would downsize the nation’s stockpile of 500 missiles, based at Air Force bases in Montana, Wyoming and North Dakota, by 10 percent, and indicated the missiles would probably come from Malmstrom.

Members of Congress from the missile states attempted to delay the withdrawals, passing legislation last fall that prevented the Pentagon from removing the weapons until a series of studies was completed. But that strategy only delayed the process for a few months, as the department has recently sent the results of those studies to Congress.

The legislation stated that the missiles could not be removed until 30 days after the studies were submitted. Josh Holly, spokesman for California Rep. Duncan Hunter, the top Republican on the House Armed Services Committee, said the committee received those documents mid-March.

That could allow the Pentagon to begin removing the missiles mid-April.

‘‘These missiles are a vital part of our nation’s defense and the Malmstrom community,’’ Rehberg said in a statement. ‘‘It’s unfortunate that this proposal has reached this point.’’

Calls to the Air Force were referred to the Air Force Space Command, which oversees the missiles. A spokesman for the Air Force Space Command would not say whether the missiles will be removed.

The Pentagon has gradually decreased the nation’s nuclear stockpile since the end of the Cold War, when the missiles were placed in the High Plains because of the region’s relative proximity to Russia. Lawmakers from the three states have argued that threats from North Korea and other countries make the weapons as important as they were 50 years ago.

The 564th Missile Squadron, 50 missiles scattered north of Great Falls, Mont., has a different operating system than all the other squadrons, requiring some different parts and training. That has led to the speculation that the ‘‘odd squad,’’ as it is dubbed, would be the one to go.

Removal of the missiles could mean the counties that house them will have less federal money to play with. The military pays for road and other infrastructure improvements in those areas.

Montana Sen. Max Baucus said the delegation would keep fighting against the cuts.

‘‘I think it’s an outrage, especially during a time when our nation’s security must be bolstered,’’ the Democrat said in a statement.

Holly, the Armed Services Committee spokesman, said the Pentagon documents submitted to the committee are classified. The law required analysis of the effects of reducing the missiles, an assessment of how many test missiles are needed to maintain the force, and a plan to complete modernization of all the missiles before the weapons could be removed.