Prague - The Czech government is ready to discuss President Václav Klaus's demand for a clause in the Lisbon treaty with the EU partners. But the government wants "an unequivocal guarantee that Klaus will sign the reform deal if the Constitutional court rules the treaty is in line with the Czech constitution, Czech PM Jan Fischer said Monday at a press conference.

"With regret the government says the condition raised by Václav Klaus now was not raised during the ratification process," said Fischer, adding that the closest date for further negotiation with the EU officials is the October EU summit.

Last week Václav Klaus, a vocal critic of the Lisbon treaty, required an opt-out from the EU Bill of Fundamental Rights.

The clause should ensure the Germans who were expelled from Sudetenland from former Czechoslovakia after the World War II will not claim property restitution.

Lawyers, including Czech government have dismissed this objection as unfounded.

The Lisbon treaty is designed to streamline the decision-making process in the EU, establishes a permanent president of the EU and foreign affairs minister.

The Czech Constitutional Court is currently reviewing complaints filed by a group of Civic Democratic senators who claim the Lisbon Treaty violates the Czech constitution. It is expected to rule in November.