Defense Secretary Jim Mattis has taken the unusual step of urging House lawmakers to reject a proposal to create a new Space Corps military service.

Mattis warned the proposal would create a "narrower and even parochial approach" to space operations, in a letter Tuesday to Rep. Mike Turner, R-Ohio, an Armed Services subcommittee chairman.

"I do not routinely comment on potential floor amendments of pending legislation. However, this particular issue warrants a response," Mattis wrote Tuesday. "I strongly urge Congress to reconsider the proposal of a separate service Space Corps."

The House is set to consider creating the Space Corps as a subsection of the Air Force as part of the National Defense Authorization Act, which could come to the floor for a vote as soon as this week.

Members of the Armed Services Committee who support the legislation cited deep problems in the structure and management of space operations, which are mostly handled by the Air Force. But Turner is proposing an amendment to strip the new service out of the bill, saying lawmakers have not done enough research or held enough hearings.

Mattis said he shares lawmakers' fears about the department's space capabilities and is working to complete a review by September.

"I look forward to working with Congress to implement necessary space organizational changes," Mattis wrote. "That said, I believe it is premature to add additional organizational and administrative tail to the department at a time when I am trying to reduce overhead."

The White House also called the House proposal "premature" in an Office of Management and Budget assessment of the annual defense policy bill.

The secretary and chief of staff of the Air Force came out strongly against the proposal last month, saying it would create more unneeded military bureaucracy and hobble ongoing efforts to modernize space operations.

Turner, who chairs the Tactical Air and Land Forces subcommittee, said the House's idea of creating a new service is an "extreme" solution to the issues with space operations and would come at a bad time, just as the new administration is trying to rebuild its military forces following several years of budget caps.

"Don't get a new secretary of defense, a new secretary of the Air Force and hand them the problems and then also hand them a legislatively compelled reorganization creating a new service branch," Turner said.

His amendment removing Space Corps from the National Defense Authorization Act was being considered by the House Rules Committee on Wednesday. The committee was set to decide whether it will get a vote when the annual defense policy bill goes to the chamber floor.

Rep. Mike Rogers, R-Ala., has spearheaded the Space Corps effort and criticized the Air Force pushback as resistance to needed change.

The Space Corps will be disruptive in the beginning but is necessary for the military organize its space efforts against fast advancing programs by Russia and China, Rogers said.

"The department can't fix itself on this, Congress has to step in," he said during Armed Services debate on the proposal late last month.