Updated from 7:45 a.m. EST

Microsoft ( MSFT) sank Thursday after its top executives failed to reach a settlement in the software maker's ongoing antitrust proceeding with the European Union.

The breakdown opens the door to the imposition of marketing restrictions and a fine when European Union Competition Commissioner Mario Monti proposes a final penalty in Brussels next week. Microsoft shares were recently down 21 cents, or 0.8%, to $24.92.

"We worked very hard to try to resolve these issues without litigation," Microsoft Chief Executive Steve Ballmer said. "Because of the tremendous value we attach to our relations with governments all across Europe, we made every possible effort to settle the case, and I hope that perhaps we can still settle the case at a later stage."

Microsoft brass, including Ballmer, were trying to avoid the ruling by reaching an accord that would have extended the marketing restrictions to a more global scale, but the two sides were unable to settle in negotiations that ended Thursday.

"We made substantial progress toward resolving the problems that had arisen in the past, but we were unable to agree on commitments for future conduct," Monti said at a news conference. "In the end I had to ... decide what was best for competition and consumers in Europe."

In a draft EU ruling, Microsoft was found culpable of engaging in monopolistic abuses of its dominant position in the software market. Among other things, regulators object to the way it packages a movie and music-playing program with its Windows operating system, which runs more than 90% of the world's computers.

"We have to ensure that the law is not just about competitors' complaints about the impact of new features," Microsoft said in a statement. "There needs to be consideration of the needs of consumers for new innovations. Consumers must be part of the equation. Perhaps the courts will provide the clarity that is necessary to resolve these issues. Today is just another step in what could be a long process."

The ceiling for EU fines is 10% of a company's global sales, which would be north of $3 billion in Microsoft's case, although nothing so large is anticipated.

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