A Fort Shafter program that expanded Army training and interaction with Asia-Pacific nations — at double the cost — has come under scrutiny by Congress, in part because of perceived similarities to the Marine Corps.

The three Pacific Pathways iterations run by U.S. Army Pacific in fiscal 2015 cost $34.5 million — about twice that of the same exercises prior to Pathways, the U.S. Government Accountability Office said in a report this month.

Launched in 2014, Pacific Pathways deploys a battalion-size task force of between 400 to 900 soldiers for about 90 days, and links three to four pre-existing exercises into a single operation. Previously, the training unit sent to individual exercises could be fewer than 350 soldiers, the GAO said.

The larger force packages come with equipment such as Stryker armored vehicles, helicopters and transport ships, and allow the Army to train more intensively with host nations as well as to practice becoming a more mobile “expeditionary” force.

“Pathways builds readiness at multiple command echelons; increases exercise complexity for partners, such as by providing more equipment to exercises; supports the rebalance of forces to the Pacific with a persistent forward presence; and allows the Army to experiment with capabilities,” the GAO cited the Army as saying.

But U.S. Army Pacific “has not conducted a comprehensive analysis that demonstrates the initiative’s value, which could better inform Department of Defense decision makers as they consider budgetary trade-offs,” according to the GAO.

When Pacific Pathways was announced in late 2013, it was described as a possible crisis response force, and some defense officials questioned whether the Army was duplicating Marine Corps specialties. The House Armed Services Committee called for the GAO review.

“U.S. Pacific Command currently has other existing capabilities that are potentially similar to those envisioned for Army units under the Pacific Pathways program,” the report said without mentioning the Marines.

Army officials in Hawaii have repeatedly said there are more than enough missions for both the Army and Marines in the vast Pacific.

Pacific Pathways has taken soldiers from the region to Thailand, South Korea, the Philippines, Indonesia, Malaysia, Mongolia and Japan. In a recent iteration, soldiers from the 3rd Brigade in Hawaii in August loaded cargo aboard the Army vessel CW3 Harold A. Clinger for exercise Orient Shield 16 in Japan.

The approach has provided opportunities to exercise mission command in “complex, real-world environments” and replicate how they might operate during wartime or disasters, the GAO said.

U.S. Army Pacific told the GAO it did not initially submit a cost-benefit analysis because the effort was viewed as an innovation to existing exercises. In fiscal 2014 and 2015, Pacific Pathways used a combination of funds from Army headquarters and U.S. Army Pacific’s own budget.

“We believe the Army should continue to support Pacific Pathways because it is an innovative way to build readiness and invaluable experience in the Pacific Command area of responsibility” without increasing permanent bases, Col. Christopher Garver, a U.S. Army Pacific spokesman, told the Honolulu Star-Advertiser on Monday.

The Defense Department said that by September, U.S. Army Pacific would improve planning to better coordinate all Army elements in Pacific Pathways, and by September 2018 it would submit an analysis to Army headquarters assessing its impact on “sustainable readiness.”