WASHINGTON - The deal looked sketchy from the start.

To outfit Afghanistan's security forces with new helicopters, the Pentagon bypassed U.S. companies and turned to Moscow for dozens of Russian Mi-17 rotorcraft at a cost of more than $1 billion.

Senior Pentagon officials assured skeptical members of Congress that the Defense Department had made the right call. They cited a top-secret 2010 study that they said named the Mi-17 as the superior choice.

Turns out the study told a very different story, according to unclassified excerpts obtained by the AP.

The Army's Chinook, built by Boeing in Ridley Park, Delaware County, was actually "the most cost-effective single platform type fleet for the Afghan Air Force over a twenty year" period, according to the excerpts.

Legislators were stunned.

More than two years since the Mi-17 contract was signed, a veil of secrecy still obscures the pact.

"So why are we buying Russian helicopters when there are American manufacturers that can meet that very same requirement?" Sen. John Cornyn (R., Texas) asked.

As recently as September, Deputy Defense Secretary Ashton Carter cited the study in a letter to House members defending the decision. Carter left his job last week.

Last year, Frank Kendall, the Pentagon's top acquisition official, and policy chief James Miller pointed to the study in a written response to questions posed by Cornyn.

Weeks after the secret study was completed, Army Secretary John McHugh wrote in a 2011 memo "that the Mi-17 stands apart."

The Pentagon denies it misled Congress.

A senior department official said the study was focused on long-term requirements and not the immediate needs of the Afghan military, which were best met by the Mi-17. Also, U.S. commanders wanted the Mi-17 because it is durable, easy-to-operate and the Afghan forces had experience flying it, according to the official.

There's no dispute heavy-duty copters capable of moving Afghan troops and supplies are essential. But the decision to buy them from Russia achieved the rare feat of uniting Republican and Democrat.

Syrian link

Overall, 63 Mi-17s are being acquired through the 2011 pact. It was awarded without competition to Russia's arms export agency, Rosoboronexport, even though the Pentagon condemned the agency after its weapons were used to "murder Syrian civilians."

No Pentagon official was made available to speak on the record.

The armed Mi-17s being purchased will replace older and less capable Mi-17s the U.S. and others had purchased from brokers and contractors through the open market and then donated or loaned to the Afghans.

The fact that the Afghan forces had years of experience flying the Mi-17 figured prominently in the Pentagon's decision.

Carter and other officials said adding the Boeing copter to the mix would burden the Afghans with having to learn how to operate and maintain an unfamiliar helicopter.

The 2010 study "specifically analyzed the opportunity for DOD to provide a US alternative to the Mi-17 for Afghanistan," according to the excerpts.

Transitioning

It outlined a transitional approach in which Chinooks being retired from the U.S. fleet would be available in late 2013 to be refurbished and then replace older Russian copters, according to the excerpts. A combination of Mi-17s and renovated Chinooks, known in the Army's nomenclature as the CH-47D, could work as well.

Proceed with caution, the study advised. Shifting too quickly from the Mi-17s could undermine progress in training the Afghan air force, the excerpts said. But the study recommended a plan for converting the Afghan forces from a "pure" Mi-17 fleet to one that uses U.S. helicopters.

The Chinook option never materialized.

An extensive analysis concluded a refurbished Chinook would cost about 40 percent more overall to buy and maintain than the Russian helicopter, the senior defense official said.

That is hard to fathom.

Boeing executives told congressional staff in late September that the cost of a refurbished CH-47D would be in the $12 million to $14 million range, according to a person knowledgeable about the discussion but not authorized to be identified.

That would make an overhauled Chinook $4 million to $6 million less than what the department is paying for Mi-17s, according to a Pentagon paper listing what it is paying for the Russian craft.