Microsoft Corp. is defending itself against charges of engaging in anticompetitive practices in Europe even as it fights to overturn an antitrust ruling in the United States.

European Union Commission spokeswoman Amelia Torres said the U.S. software giant had submitted a written response Friday to charges that it had deliberately discriminated in licensing software to competitors.

The company might still request an oral hearing before the commission, but hadn’t done so as of Monday, she said.

Microsoft spokeswoman Tiffany Steckler in Paris declined to comment Monday on details of the company’s defense but called the charges “unfounded.”

The commission will now review Microsoft’s response, with no deadline for producing a decision, Torres said. Such cases can take months or longer.

The legal action began in August after a complaint by Palo Alto, Calif.-based Sun Microsystems Inc., which charged the Redmond, Wash.-based Microsoft had withheld crucial software codes and other information necessary for competitors to make compatible servers.

Since servers connect personal computers together in a network, it is crucial that their software work with Microsoft’s Windows, which has a virtual monopoly in the PC software market.

If the commission finds there was antitrust abuse, it is empowered to fine a company up to 10 percent of its annual global sales, although in practice such fines have never exceeded 1 percent.

The commission could also force Microsoft to disclose its interfaces to ensure interoperability.

In the U.S. case, a judge ruled in June that Microsoft had abused its monopoly power to suppress competition. He ordered it broken up into two companies: one selling the Windows computer operating system, and the other in charge of Microsoft’s other software and Internet products.

Microsoft is appealing that ruling.