Some of Boeing’s strongest congressional supporters are urging Defense Secretary Robert Gates to slow down the selection process for the Air Force’s new aerial refueling tanker.

Several lawmakers said in a letter to Gates that they “remain very concerned about the overly aggressive time line” to issue a new request for bids for the tanker competition. The letter was expected to be sent late Friday.

The competition to win the $35 billion tanker contract has pitted Boeing against a team of Northrop Grumman and EADS North America. The two factions are engaged in an intense lobbying war on Capitol Hill and the Pentagon. 

The Air Force initially awarded Northrop Grumman the contract, but Boeing successfully petitioned the Government Accountability Office (GAO) to re-examine the decision.

GAO found that the Air Force made “significant errors” in awarding the contract to Northrop and EADS, the parent company of Airbus, Boeing’s bitter rival in the aircraft market.

With controversy surrounding the Air Force’s decision, Gates tasked the Pentagon’s chief weapons buyer, John Young, with the selection of the tanker, taking the decision out of the Air Force’s hands.

For what will be the third go-round to select a tanker in seven years, the Pentagon implemented an aggressive selection schedule that now does not sit well with some lawmakers, particularly those hailing from states in which Boeing has a significant presence.

Boeing has already signaled dissatisfaction with the first steps the Pentagon has taken to redress the controversial issue. The Pentagon released a so-called draft request for proposals last week, which basically amends the initial request to account for GAO’s recommendations, Pentagon officials said.

But Boeing supporters are signaling that the draft request appears to favor Northrop Grumman’s offering of a larger plane, the A330. Boeing was competing with its 767, but may consider a larger version of that plane or the 777 for the competition.

On Saturday, Boeing executives are supposed to meet with defense officials for a second time this week at the Wright-Patterson Air Force Base in Dayton, Ohio.

Boeing and Northrop Grumman Corp. executives already met with Pentagon officials on Aug. 12 in Dayton, but after the meeting Boeing said it wanted more discussions, while Northrop said it was pleased with how the process was shaping up.

The Pentagon is planning to make a final decision on the tanker by the end of the year, before the end of the Bush administration. By Oct. 1, the Pentagon wants to release the final request for bids.

But to some lawmakers, the process is too rushed.

“We believe that the current rush to come to agreement on a revised RFP [request for proposals] is putting at risk the third opportunity for a successful decision,” the lawmakers wrote to Gates. “Congressional staff were briefed just last week on components of the revised RFP yet many questions remain unanswered, such as military construction costs, especially for Air National Guard units and the states that support the aerial refueling mission.”