Several senators and congressmen echoed the criticism leveled at Brussels a day after the European Commission ordered a 497 million euro (613 million dollar) fine and changes to the Windows operating system by the software titan.

Senator Richard Lugar head of the Foreign Relations Committee, said in a statement he was "troubled" by the decision, which came in sharp contrast to a US settlement of an antitrust action against Microsoft.

"This breakdown in trans-Atlantic cooperation is likely to have ripple effects that will do harm to the trade and economic relationship between the United States and the European Union," Lugar said.

"The Commission's action will be felt worldwide, resulting in conflicts in the area of international competition law."

Senate Majority leader Bill Frist said the move could lead to "a new trade war" adding that the European Commission ruling against Microsoft" is the first shot."

"In imposing this anti-consumer, anti-innovation penalty, the Commission has blatantly undercut the settlement that was so carefully and painstakingly crafted with Microsoft by the US Department of Justice and several state antitrust authorities," Frist said.

"There can be no question that the US government was entitled to take the lead in this matter -- Microsoft is a US company, many if not all of the complaining companies in the EU case are American, and all of the relevant design decisions took place here."

Ten members of the House International Relations voiced similar concerns in a joint statement.

Representative Robert Wexler said that the EU decision "sets a harmful precedent for other countries in the area of competition policy -- particularly given that the US and EU signed a Comity Agreement on competition laws in 1991, which was reaffirmed and strengthened in 1998."

"It is imperative that we maintain America's competitiveness," said Peter King, another of the 10 congressmen.

"Today's ruling undermines the US/EU Comity Agreement and will deter US companies from participating in European markets. The EU should reconsider its ruling and follow the Comity Agreement."

The US Department of Justice said Wednesday's EU antitrust ruling on Microsoft was "unfortunate" and could have unintended effects on the marketplace.

"Imposing antitrust liability on the basis of product enhancements and imposing 'code removal' remedies may produce unintended consequences," the department's antitrust chief R. Hewitt Pate said in a statement.

"Sound antitrust policy must avoid chilling innovation and competition even by 'dominant' companies. A contrary approach risks protecting competitors, not competition, in ways that may ultimately harm innovation and the consumers that benefit from it."

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