Microsoft faces further litigation after nine of the 18 states suing the firm refused to accept the settlement agreed with the US Department of Justice (DoJ).
Connecticut, Iowa, California, Florida, Kansas, West Virginia, Utah, Massachusetts and Minnesota have decided to continue the antitrust litigation against Microsoft.
New York, Illinois, North Carolina, Kentucky, Michigan, Ohio, Wisconsin, Louisiana and Maryland have approved a revised settlement which they negotiated with the software giant.
Connecticut state attorney Richard Blumenthal explained that the nine states that have parted company with the federal government want tougher penalties and remedies against Microsoft.
"I believe this agreement reflects very good progress, but it may not be good enough to protect consumers against misuse of monopoly or recurrence of violations of law," he said.
Massachusetts and California have said that the settlement is too soft on a company that has been found to have illegally maintained its monopoly in PC operating systems.
Massachusetts Attorney General Tom Reilly, the first to oppose the deal, said: "The agreement reached by the DoJ and Microsoft is fundamentally flawed. It has enormous loopholes and may prove to be more harmful than helpful to competition and to consumers."
US District Judge Colleen Kollar-Kotelly has said she will hold separate parallel proceedings in the case next year. One will determine whether the proposed agreement is in the public interest and a second will consider the dissenting states' decision for tougher remedies.
Microsoft chairman Bill Gates said in a statement: "We are pleased that a number of states have joined the DoJ in supporting this settlement.
"The fact that so many states have joined the federal government in supporting this agreement is a very significant, positive step toward resolving these issues once and for all."
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