The commission's competition representative said that if the matter is not resolved within a matter of weeks, it may fine Microsoft a significant sum of money.
"Our patience is in terms of weeks rather than months," said the representative. "They've had over a year now. Microsoft knows that if they don't comply to our satisfaction, we can fine them up to five percent of their (daily global) turnover every day."
He said that Microsoft was aware of the specific date by which it must comply with the ruling, but the EC has decided not to publicize the date as a "negotiation tactic."
The initial antitrust ruling, delivered on March 24, 2004, demanded that Microsoftto rival server-software makers that would allow them to design products compatible with Windows. The commission also required Microsoft to offer a version of Windows without Windows Media Player, so that other media-software makers could more fairly compete in the market.
The EC rejected Microsoft's proposed solution to the server interoperability in March this year, citing four concerns. One of its main objections was the high level of royalties that Microsoft had proposed, the representative said. "The level of royalties should reflect the degree of innovation in the product, rather than (Microsoft's) monopoly power," the representative said.
Although Microsoft announced last month that it had addressed the majority of the Commission's concerns in this area, the EC representative said the European body was still talking to the software giant "concerning the proper implementation of the interoperability remedy." There are also issues regarding the version of Windows without Media Player that are yet to be resolved, the representative said.
A Microsoft representative declined to comment on the deadline that the EC has imposed or the company's work toward complying with the ruling.
"I wouldn't want to talk about timing or what the dialogue is about," the Microsoft representative said. "We continue to work diligently and quickly to resolve the outstanding issues."
The EU competition commissioner Neelie Kroes met Microsoft CEO Steve Ballmer at the end of April to discuss the software giant's failure to comply with the ruling. Kroes said Microsoft must comply with the decision "urgently and in full."
Ingrid Marson of ZDNet UK reported from London.