Seven US states have asked for a continuation of government oversight on Microsoft's activities in an effort to curtail possible monopolistic behaviour.

California, Connecticut, Iowa, Kansas, Minnesota, Massachusetts and the District of Columbia have asked a federal judge to extend oversight of Microsoft for another three years.

The oversight was implemented after Microsoft reached a settlement with the US Department of Justice over its bundling of Internet Explorer, but this is due to end in November.

Stephen Houck, an attorney representing the State of California, maintained that an extension is needed to monitor Microsoft's practices with its new Vista operating system.

Reports in Associated Press said that Houck had told US Judge Colleen Kollar-Kotelly that it would be "short-sighted to end the final judgements just now".

Those representing other states also highlighted Microsoft's continuing dominant role in the PC market, along with fears that the firm might use other monopolistic practices to stamp out the opposition.

If the consent decree is allowed to expire, the states said that the " principal constraint on Microsoft's ability to abuse its market power will be gone".

But the judge seems likely to lift the oversight, as she said that it was never intended to reduce Microsoft's market share and that the company is on course to satisfy all the terms of the oversight provisions.

Jack Evans, a spokesman for Microsoft, said: "We are a bit surprised that a few states are now requesting an extension given that they previously called the settlement ineffective."