SEOUL: US software giant Microsoft has lost a legal battle with a South Korean firm over its flagship Office software, officials said Monday. The Supreme Court in a ruling last week rejected a request from Microsoft to nullify patents obtained by Hankuk Aviation University professor Lee Keung-Hae in 1997.

The court ruled that the patents apply to technologies which automatically switch the input mode between Korean and English. In 2000, Lee and the company acting as his agent - P and IB - filed a damages suit against Microsoft Korea for patent infringement but the case remained unsettled at an appeals court after the US company filed a separate lawsuit insisting the patents should be invalidated.

"The decision on Friday will strengthen our position in a fight to win the pending damages suit," P and IB head Kim Kil-Hae told AFP.

"Microsoft has used our technologies without paying software royalties to our side," he said. "Microsoft should stop selling its Office suite incorporating the language-switch solution and accept our demand for compensation," he said, estimating the amount due from Microsoft to be 70 billion won (75 million dollars).

Microsoft refused to accept the demand.