Microsoft's antitrust battles are threatening to engulf the entire US computer industry as new allegations and counter-charges involving several of the industry's largest companies are dragged into the case.

Less than two weeks before the scheduled start of the landmark antitrust trial against Microsoft by the US Justice Department and 20 state attorneys-general, the complex relationships between the software giant's rivals and partners are coming under increased scrutiny.

The software giant has issued subpoenas to Apple Computer, IBM, Intel, Netscape Communications, Novell, Oracle, Sun Microsystems and others demanding information about their "efforts to collaborate in competition with Microsoft". The companies have been "doing everything Microsoft is doing, and possibly more", the company said.

Microsoft said it had issued the subpoenas in response to "new and groundless allegations" introduced by the Justice Department last week. In a move to bolster their case against the software group, prosecutors added charges that the company had used its monopoly power to pressure Intel, Apple and others to drop multimedia software development efforts.