The Army risks wasting as much as $1.8 billion developing a replacement for the M4 carbine that it may not need, according to the Pentagon’s inspector general.

The carbine replacement program is one the Army and Pentagon “may want to re-evaluate,” because the service is “seeking to acquire more rifles during a time when their total force structure will be reduced,” Lynne Halbrooks, principal deputy inspector general, said in a statement provided Tuesday to a House committee. The Pentagon plans to reduce Army ground forces to 490,000 by 2017 from about 560,000 in 2011.

Colt Defense, based in West Hartford, Conn., is the primary supplier of the U.S. Army’s M4 rifle and would face competition under the replacement program.

The carbine replacement is among programs Halbrooks highlighted as having questionable value in the statement to the House Committee on Oversight and Government Reform.

The panel is reviewing opportunities to reduce waste and improve efficiency at the Pentagon because most of its 800,000-person civilian workforce faces one unpaid furlough day per week, from late April through Sept. 30. The department is in line for $500 billion in spending cuts over a decade on top of $487 billion that was already planned.

Halbrooks said the Pentagon and the Army need to re-evaluate the carbine replacement program because they’re seeking to develop the new rifle at the same time as the service is modifying the current M4 weapon.

The Army carbine program is an example of decisions the Pentagon and military services face in culling savings from the projected $27 billion expected to be spent in fiscal 2012 on major acquisition programs.

“As budgets continue to come under increasing scrutiny, the department must continue to evaluate the merits, additional capabilities and cost” of major acquisition programs, she wrote.