FORT RUCKER, Alabama - Defense Secretary Robert Gates said he expects U.S. Senate movement soon on the nomination of Ashton Carter as the Pentagon's chief arms buyer.

I have every hope and expectation that Dr. Carter's nomination will be moved in the near future, Gates told reporters at Fort Rucker, home of the Army's main site for training pilots and unmanned aerial system operators.

The Senate Armed Services Committee earlier this month approved Carter's nomination. But several senators have put a hold on it, citing concerns about the delayed $35 billion competition between Northrop Grumman Corp and Boeing Co to build 179 new aerial refueling tankers.

Gates said he hoped to move forward on the tanker competition soon, and would let lawmakers review the proposed competition criteria and get their input before releasing the terms of a revamped competition.

Gates questioned congressional moves to block Carter's nomination, especially since many lawmakers were pressing the Pentagon to undertake acquisition reforms -- a job that Carter would largely oversee.

At a time when most of the Congress believes there is a need for acquisition reform in the Department of Defense, to delay the confirmation of the person who is most needed in that effort clearly is counter-productive, Gates told reporters.

This will be the Air Force's third attempt to replace its aging fleet of KC-135 refueling planes, which are more than 50 years old on average.

Congress in 2004 killed the first bid after an Air Force plan to lease and buy 100 Boeing 767s failed amid a major procurement scandal.

The Air Force then held a new competition and awarded a $35 billion contract to Northrop and its European subcontractor, Airbus parent EADS, in February.

But Gates canceled the deal last fall after congressional auditors found problems in the Air Force's handling of the competition, and the process became very politicized.

On Tuesday, Gates said he hoped that a new tanker contract could be awarded by early next year or next summer. They're desperately needed by the Air Force, he said.

Gates, the only member of former President George W. Bush's cabinet who stayed on under President Barack Obama, reiterated his opposition to buying more tankers each year and splitting the procurement between the two companies.

He said that would increase logistics, training and maintenance costs over the long run. Development costs alone would likely double from $7 billion to $14 billion, he said.

Carter, a Harvard University professor and former assistant secretary of defense for international security policy, was nominated for the job of overseeing more than $100 billion in annual U.S. arms purchases and a $70 billion research enterprise. If confirmed by the Senate, Carter would replace John Young as undersecretary of defense for acquisition, technology and logistics.

Senators Jeff Sessions and Richard Shelby, both Republicans of Alabama, where Northrop had planned to build its A330-based tankers, have put a hold on the Carter's nomination.

The senators say they have unanswered questions about how open and transparent the next competition will be.

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