Norwegian browser maker Opera urged European Union antitrust regulators on Monday not to rush to close its antitrust case against Microsoft before ensuring a level playing field among browsers.

European Competition Commissioner Neelie Kroes said in a newspaper interview last week that she was keen to reach a deal with Microsoft before her term ends this year. A settlement would end the company's decade-long dispute with the European Commission. We are slightly concerned about perhaps a premature settlement in this case, Opera's Chief Technology Officer Hakon Wium Lie told Reuters in an interview.

We are also eager to close the case but we want to make sure the settlement is effective. We think the current solution on the table will not be an effective settlement, he said.

Opera had in December 2007 complained to the Commission about Microsoft's tying of its Internet Explorer browser to its Windows operating system, triggering formal charges from the Commission against Microsoft in January this year.

The EU competition watchdog is now reviewing feedback from Microsoft's rivals and other interested parties on the U.S. software company's proposal to install a ballot screen that would give users the chance to choose its competitors' Web browsers.

The Commission has to date slapped a total 1.68 billion euros in fines on Microsoft for infringing EU antitrust rules.

(Reporting by Foo Yun Chee, editing by Marcin Grajewski)