It's just like playing a card game where one player decides to change the rules once the cards are known

Yves Robins, Dassault

While the South Korean government declared an open evaluation process, Dassault has alleged that the rules have been changed to make sure that US-based Boeing gets the nod.

The US has been the biggest military supplier to South Korea since the Korean War ended in the 1950s, and has provided all the country's fighters to date.

Dassault has applied to the Seoul District Court to freeze the process and force South Korea's Defence Ministry to reveal how its decision is being made.

Playoffs

Seven companies were involved in the initial stage of the evaluation process, with four - assault, Boeing, the European Eurofighter consortium, and Russia's Sukhoi - chosen to compete in the second round.

The bids were judged through scores awarded on criteria such as performance, price, and the amount of technology to be transferred.

The Eurofighter Typhoon and the Sukhoi SU-35 proposals have both been rejected.

But the government said that Dassault's Rafale and the Boeing F-15K, the latest version of an aircraft in service since shortly after the Vietnam War a quarter of a century ago, scored within 1.1% of one another.

According to a rule change made in December, political considerations can take priority in the resulting "play-off", which is scheduled to be completed by the end of April.

Changing the rules

But Yves Robins, Dassault vice-president for international affairs, compared the rule change to "playing a card game where one player decides to change the rules once the cards are known".

Yves Robins: "Like a card game"

Dassault's deal offered more technology transfer, a plane a generation newer and a price tag that was $350m less, Mr Robins said.

"It's incomprehensible that the difference (in the deals) is only 1.1%," he told BBC News Online.

The only conclusion was that the process has been rigged as a way of preserving the strategic relationship with the US, Mr Robins said.

Tensions

Dassault's move followed claims reported in the Korean media that the Defence Ministry had attempted to force a test flight team to choose the F-15 even though the aircraft was beaten in flight tests.

The air force colonel who made the allegations was later arrested for leaking secrets.

"No-one would have reproached the Koreans if they had said that for political reasons they wanted to go with the US," Mr Robins said.

"They're a sovereign country and it's their decision.

"What's dishonest is to start an international competition pledging fairness and then, when the result is not one you would consider politically correct, to change the rules in order to make the result look like a technical decision."

The fighter project is now in its fifth year, having originally been conceived in 1997 and shelved due to the Asian currency crisis.

Some Seoul politicians are pressing for further delays, as military expansion plans are hurting relations with communist North Korea.