Prague - Top leaders of four of the five EU heavyweights - Britain, Italy, France and Spain - are to skip the bloc's Thursday high-level summit aimed at boosting ties with six ex-Soviet states, a flagship initiative of the Czech Republic's presidency of the European Union.

Outgoing Czech Vice-Premier for European Affairs Alexandr Vondra confirmed Thursday that French President Nicolas Sarkozy, British Prime Minister Gordon Brown and his Italian and Spanish counterparts, Silvio Berlusconi and Jose Luis Zapatero, would not attend, a sign, analysts said, that the event carried little importance for them.

The leader for the fifth of the EU's largest players, German Chancellor Angela Merkel, is to attend the summit with Armenia, Azerbaijan, Belarus, Georgia, Moldova and Ukraine. Vondra said that she is to play an "important" role.

The EU's executive, the European Commission, is to be represented by its top man, European Commission President Jose Manuel Barroso, the presidency said.

Vondra said that the absences would send the wrong signal to new member states on the Lisbon Treaty, the EU's reform pact aimed at streamlining decision-making through institutional reform, which critics fear will be a boon for the EU heavyweights.

"I would expect them to come on May 7 when there was a vote on May 6," Vondra said referring to Wednesday's long-awaited final vote on the EU accord in the Czech Republic's bicameral parliament.

Following a series of delays, the Czech Senate was the last parliamentary chamber in the EU to vote on the pact, which has been stalled since Ireland turned it down in a June 2008 referendum.

A day before his cabinet's departure, Vondra had especially harsh words for Sarkozy, who has criticized the Czech EU presidency as inadequate to chair the bloc at a time of global economic crisis.

"His imperial style of presidency did not make our team presidency easier," Vondra said. "You don't know what you can expect when he's getting up in the morning."

The presidents of two partner countries, Belarus' Alexander Lukashenko and Moldova's Vladimir Voronin, are also to skip the launching event of the so-called Eastern Partnership.

Despite their absence, Vondra described the representation of the six partner countries as "on the highest possible level." "The level of participation from Moldova and Belarus is adequate. That's what we expected," he said.