Microsoft is asking the US Court of Appeals for the Federal Circuit to allow it to keep selling Word software as it fights an unfavourable patent ruling.
The US District Court for the Eastern District of Texas found Microsoft infringed on a patent held by a Canadian company, i4i LLP.
Last week, the judge ordered Microsoft to pay $290 million and to stop selling copies of its word processing program that use the patented technology within 60 days.
The patent relates to the way Word 2003 and 2007 let users customise document encoding.
Microsoft says it and the public will both suffer if Word goes off the market while the company devises a workaround.