Microsoft has engaged in a fresh war of words with the European Commission over the launch of its new Windows Vista operating system in Europe.
The software giant suggested Brussels' vigorous attempts to force it to comply with anti-trust rulings could lead to delays in Vista's European launch.
Brussels said the firm's comments were "misleading" and that it was its duty to comply with competition laws.
The already delayed software program is due to be launched in January.
Microsoft has been locked in a bitter struggle with the European Commission over its business practices for years.
It was fined $640m for anti-competitive behaviour in 2004 and was hit with a $357.5m penalty earlier this year for failing to meet Commission demands for it to share technical information with other firms.
Vista is not under formal scrutiny but competition commissioner Neelie Kroes wrote to Microsoft earlier this year outlining potential concerns about features of the system.
Functions highlighted included its integrated Internet search facility and software capable of creating fixed-document formats.
Microsoft said Brussels had not answered a request for guidance on what it needed to do to ensure Vista did not fall foul of regulatory problems.
In response, the Commission said it sent detailed information to Microsoft in July and the US firm had only replied last week.
Microsoft said it was too early to tell whether Brussels was "seeking additional product design changes (to Vista) that would result in delay in Europe".
But Brussels said it had given Microsoft specific competition guidance on many occasions and was continuing to do so.
"It is not up to the Commission to give Microsoft a definitive 'green light' before Vista is put on the market," said a Commission spokesman.
"It is therefore misleading to imply that the Commission could be the cause of delays in launching Vista in Europe."
Microsoft hoped to release Vista - the first major update to its operating system since Windows XP was introduced five years ago - in the second half of 2006 but the launch date was put back.
There has been recent speculation that Vista could be further delayed.