San Francisco - Microsoft and US authorities on Thursday jointly proposed an 18-month extension of federal court supervision of the company's business practices, but said it was likely that no further action would be necessary to enforce the 2001 settlement of the government's antitrust lawsuit.

The Department of Justice and 17 states that had filed the antitrust suit said the extension was needed to review technical documentation that helps other companies write software that works with Microsoft's dominant Windows operating system.

The extension would also allow the courts to oversee the release of the next version of Microsoft's operating system Windows 7.

The court restrictions had been set to expire November 12 but will now continue to May 2011. The court decree had previously been extended for two years beyond its original November 2007 expiration date.

Government antitrust enforcers "concluded that an 18-month extension of the final judgments is appropriate and necessary," said the joint status report filed with US District Judge Colleen Kollar- Kotelly in Washington.

She has scheduled an April 22 hearing in the case. State antitrust enforcers also said that Microsoft "has made significant modifications to those marketing programs" that alleviated their concerns and that the 18-month extension "was long enough to allow for a reasonable degree of confidence that additional extensions will not be necessary."