The European Commission said on Wednesday it told Microsoft that it had competition worries about the firm's new operating system Vista, another antitrust concern that the software giant must answer in Europe. He said although there was no formal investigation into this issue, the Commission expected Microsoft to react. The EU executive will open separate proceedings against the company should it find that the operating system broke competition laws.

"We assume Microsoft has its own interest at heart and it wants to launch another product without having to worry about the Commission instituting various actions under antitrust law because of this product," Todd told a news briefing.

The European Union's top competition regulator has warned Microsoft it won't be allowed to sell its new Vista operating system in Europe if it comes pre-loaded with certain features, the Wall Street Journal said on Wednesday.

Neelie Kroes, the EU's antitrust commissioner, told the newspaper she sent a letter last week to Microsoft Chief Executive Steve Ballmer citing concerns similar to those in the dispute between the EU and Microsoft over other Microsoft software packaged with the company's current Windows operating system.

The EU letter follows Microsoft's announcement last week that it would delay release of Vista until January due to a need for more tests of the software.

A Microsoft spokesman told the paper his company was not aware of the March 20 letter and was therefore unable to comment.

A spokesman for Kroes said the EU is concerned about Microsoft's plans for Internet searches, but did not elaborate, the report said. Google Inc and other Internet-search services have said they are concerned Microsoft could use its Internet Explorer 7 Web browser to unfairly direct computer users to Microsoft's own search service, the Journal said.