A five-year extension of large portions of the US antitrust judgment against Microsoft isn't needed and the reasons a group of states have given for continuing oversight won't fix the problems they still see, the US Department of Justice said in a court brief filed Friday.

The DoJ's 12-page brief opposes an extension of the antitrust judgment, signed by the company and regulators in 2002, until November 2012. A group of states has asked District Court Judge Colleen Kollar-Kotelly to extend the antitrust judgment, but the DoJ has said it would oppose an extension.

The states haven't made the case for an extension, DoJ lawyers wrote in Friday's brief. A group of states led by California argued that ongoing court monitoring of Microsoft is needed to "pry open" the OEM (original equipment manufacturer) market to web browsers that compete with Microsoft's Internet Explorer.

"They make no showing, however, that any conduct by Microsoft has foreclosed the OEM channel to third-party browsers," the DoJ lawyers wrote. "Rather, they simply state that to date, no OEM has shipped a non-Microsoft browser as the default web browser. The final judgments do not mandate that OEMs, who are not parties in this case, install non-Microsoft web browsers as a default."

The California group of states also asked Kollar-Kotelly to extend the judgment to prevent Microsoft from abusing its monopoly power in the future. But the judgment was focused on past conduct, the DoJ wrote.

An extension "based on potential future misconduct by Microsoft is not supported by law," the DoJ said.

The DoJ brief also questions the decision by four states – New York, Maryland, Louisiana and Florida – to join the call for an extension after they sided with the DoJ in an August report suggesting the antitrust judgment had been effective. Nothing has changed to warrant this "about face," the DOJ said.

Microsoft has agreed to an extension of the section of the judgment requiring it to make its communications protocols available to other software vendors. Microsoft's efforts to fix technical documentation for the protocols have run into several delays. In the August 2006 agreement, that portion of the judgment will remain in effect for at least two years.

In September, the California group of states asked for an extension of all the middleware portions of the antitrust judgment, except for a section that governs the royalties Microsoft can charge PC manufacturers for the Windows operating system.

Stephen Houck, a lawyer for the California group, argued then that Microsoft retains a huge lead in the operating system and web browser markets.

"Microsoft continues to have a stranglehold over the two products that nearly all consumers use," he said during an antitrust compliance hearing in US District Court for the District of Columbia. "Very little has happened in five years in those markets."