The US judge overseeing the Microsoft antitrust case will release his final ruling at 4.30pm (EDT - 9.30pm BST) this evening. It is widely expected to include an order to break up Bill Gates's company.

US district judge Thomas Penfield Jackson ruled in April that Microsoft had broken antitrust laws. He is now believed likely to back the US justice department's plan to divide the corporation into two companies, one making and selling operating systems for personal computers such as Windows and the other containing Microsoft's other software and online businesses.

At a hearing last month, Judge Jackson requested only minor changes to the government plan, leading many antitrust experts to believe he is receptive to the proposed break up.

Microsoft has said a break up would be bad for consumers and has vowed to appeal against any such ruling. The company has predicted that it will prevail on major points.

"A break up of Microsoft, I think, would be an awful thing for consumers and for the industry. The real issue in a possible break up would be the harm it does to innovation," chief executive Steve Ballmer said in Oslo.

"But we'll be fine either way," he added.