Australia will decide at the end of this year on the timing of an order for an initial 12 F-35s while it considers options to replace 71 early model F/A-18 fighter jets and a recently retired fleet of 24 Vietnam-era F-111 supersonic bombers.

Many defence insiders expect plans for a fleet of F-35s to be revised to feature 48 Super Hornets - 12 equipped as EA-18G Growlers with radar-jamming electronic weapons - and as few as 50 Joint Strike Fighters.

A source familiar with the matter said Canberra’s decision on the Super Hornets could come within the next three to six weeks.

“The Super Hornets will eat into F-35 orders,” said Sam Roggeveen, a former Australian government intelligence and arms analyst, now with the Lowy Institute security think tank.

“It’s not too crude to say it will be a one for one replacement, because so far that’s the kind of basis that defence has so far been working on anyway.”

Budget cuts have already forced Italy to scale back its F-35 orders, and Turkey has delayed its purchases by two years. Orders from Japan and Israel have buoyed the project, and additional Israeli orders are expected in 2013.

Singapore has also taken a more active interest in the radar-evading jet, and South Korea is expected to announce a winner in its fighter contest late this year.

Australia and other countries are watching orders and problems with the jet with concern, since every reduction drives up the price of the remaining fighters to be built.

“It is a nuisance,” said a spokesman for the Dutch defence ministry, which has already paid for two test planes but will determine the size of its total F-35 order later this year.

Australian officials know the stakes are high.