The US Defense Department on Tuesday defended its bidding practices as fair after Europe and some US lawmakers charged that contract rules threw a major military deal to Boeing.

"One would not expect us to apologize with respect to getting the taxpayer the best aircraft for the capabilities that the air force has asked for," Pentagon spokesman Bryan Whitman told reporters.

US aerospace giant Boeing is poised to win a 35 billion-dollar contract to build an aerial refueling tanker plane for the air force after Northrop Grumman and European partner EADS bowed out.

Northrop Grumman said that air force requirements for the tanker program published last month favored Boeing and insisted that its larger tanker had greater capabilities at a competitive price.

But Whitman said it was up to the Defense Department to decide what it needed.

"To suggest that we should conduct a competition that would result in the department paying a much higher price for capabilities that are not needed isn't effective competition," he said.

"We're going to define what the requirements are and we're going to buy to those requirements," he said. "We're not going to buy more capability than what we need either; we're not going to buy less capability than what we need."

A German government minister accused the United States of "protectionism" and said Berlin would take up the issue at the political level and at the World Trade Organization.

A French foreign ministry spokesman also warned that Paris will study closely the "possible implications" of the dispute.

Some US lawmakers were also upset. Representative Howard McKeon, the top Republican on the House Armed Services Committee, called on Northrop to get back in the race.

The Northrop-EADS team originally won the contract in February 2008, but the deal was cancelled after Boeing successfully appealed the decision to the investigative arm of Congress.