Brno, Czech Republic - The Czech Republic's top court threw out a challenge to the European Union's reform treaty Wednesday, removing a key obstacle in the only nation that has not ratified the pact.

The Constitutional Court ruling clears the way for Czech lawmakers to consider the Lisbon Treaty before the Central European nation takes over the six-month EU presidency on January 1.

Czech President Vaclav Klaus, a fierce critic of the treaty and of deeper European integration, has the final say on the pact. He said this week he would sign it only after Ireland reverses its rejection.

The treaty, designed to ease decision-making in the 27-member EU and strengthen it as a global player, has been stalled since Irish voters turned it down in a June referendum.

A group of eurosceptic Czech senators filed the court challenge on elements of the treaty that they said are in breach of the Czech constitution.

The 15-member court's opinion countered that EU integration was not taking place "in a radical manner that would translate into a loss of sovereignty, but it is an evolutionary process", Justice Vojen Guttler said.

Klaus declined to say whether he would put the treaty back before the court, but expressed hope that lawmakers would.

"I expect some group of lawmakers or Senators to raise these arguments again and that they will raise other arguments, not just mine," he told reporters after the ruling.

Even if both houses of the Czech parliament approved the treaty, Klaus would have no deadline to sign it.

He argued before the court on Tuesday that the treaty was at odds with the Czech constitution as it infringed on the country's sovereignty.

Klaus on Wednesday attacked the verdict as political and sealed long before his appearance at the court.

The Lisbon Treaty needs approval in all EU member countries to enter into force. Ireland was the only member state that called a referendum.

While at the helm of the EU, the Czech Republic is likely to negotiate with Ireland on ways to overcome the rejection.

Prime Minister Mirek Topolanek, who unenthusiastically signed the accord for the Czech government in December 2007, issued a lukewarm welcome to the court's verdict.

"It enables both chambers of the parliament to continue the ratification process; however, I still expect an expert and public debate to continue," he said in a statement.

Topolanek has called the pact a compromise whose only alternative is withdrawing from the EU and expressed hope that it could clear parliament before the Czech Republic starts chairing the EU.

The treaty would replace the EU's rotating presidency with an elected president, create the post of a de-facto foreign minister, strip members of veto rights in most fields and make the EU's Charter of Fundamental Rights legally binding for member states.

The treaty, which was approved by parliaments in all member states except for the Czech Republic, awaits presidential signatures in Germany and Poland.