But Prime Minister John Howard was unfazed by the problems surrounding development of the 240 billion US dollar Joint Strike Fighter (JSF), saying the new generation warplanes were "a fantastic aircraft concept".

Howard, one of US President George W. Bush's closest foreign allies, chose the yet-to-be-built JSF over a rival European fighter to replace Australia's ageing air force fleet in the biggest military procurement project in Australian history, believed worth 16 billion dollars (11.5 billion US).

The Australian newspaper, in a front-page article Thursday, said cost overruns, design flaws and production delays were undermining support for the JSF in the US congress.

It notably said the JSF model was some 680 kilograms (1,500 pounds) overweight in the design phase -- a flaw that could curtail the aircraft's ability to carry out effective combat missions.

The Australian air force's director-general of new combat capability, Air Commodore John Harvey, told the newspaper the setbacks were problematic, but would not prevent completion of the JSF project.

"The situation is disappointing regarding the costs and schedule issues, but at the end of the day it will still be a very good aircraft and we expect it to suit our needs," he said.

Responding to the report, Howard expressed confidence in Australia's plan to buy up to 100 of the JSF aircraft, in which the government has already invested 150 million US dollars.

"Cost blowouts do occur and have always occurred in every country in relation to the development of new technology connected with new weaponry," Howard said in a radio interview.

"It's a fantastic aircraft concept, it really is, and it will give an enormous defence reassurance to the Royal Australian Air Force when we get it," he said.

Australia plans to use the JSF to replace its aging fleet of US F/A-18 fighters and F-111 bombers, but the number of aircraft it ultimately purchases could depend on how high their price rises.

Current defense plans are built around a timetable of receiving the first JSF in 2012, but delays in the production could force the air force to lease an interim fighter from another country or pay more to keep its existing planes in the air.

WAR.WIRE