SAN FRANCISCO — Microsoft Corp. faces the possibility of having to halt US sales of its flagship Word software after a Toronto technology company won a lawsuit that, if upheld, could bar the company from selling the product.

On Tuesday, a US district court in Texas issued a permanent injunction that bars Microsoft from selling recent versions of its Word software because it violates a patent held by i4i Inc. Judge Leonard Davis also awarded the Canadian company damages of roughly $290 million.

Microsoft, in a statement, said it would appeal the verdict. It must appeal within 60 days of the judgment.

The judgment follows a jury decision on May 20 that found Microsoft had willfully infringed on an i4i patent for software that manipulates “document architecture and content.”