Prague - Czech Prime Minister Mirek Topolanek's party lost the Senate run-off elections Saturday in a defeat that could reshape the Czech Republic's EU presidency in the first half of next year.

The loss could topple the premier and empower vocal European Union critic President Vaclav Klaus, just weeks before the country takes over at the helm of the 
27-member EU bloc on January 1.

Analysts said a boost to the followers of the eurosceptic president could weaken the Czech presidency.

"The EU has already indicated that it does not take the Czech presidency seriously," said political scientist Jiri Pehe, who heads the Prague branch of New York University.

"If the government becomes more eurosceptic, the EU will cut us off," he said. "It would not let (Klaus) to carry out his sabotage."

The election result, however, would do nothing to hamper two key foreign policy projects of Topolanek's center-right government - the EU's reform Lisbon Treaty and accords on hosting a US missile defence base.

Official results showed that Topolanek's Civic Democrats lost their absolute majority in the upper house, which would have allowed the party's eurosceptics to block the Lisbon Treaty.

Topolanek's party won three seats but needed to defend nine to retain the absolute majority of 41 in the 81-member Senate.

Topolanek's arch-rivals, the main opposition Social Democrats, triumphed in 22 races, for the first time since the Senate came to existence in 1996, while the Communists won one.

Still, those gains did not boost the leftist opposition enough for their senators to torpedo the plans for placing the US missile defence radar base on Czech soil.

Voters were choosing 26 senators this week. One Senate race was already decisively won by a Social Democratic candidate in the first round of voting last week.

Voters issued the governing parties a stern report card for unpopular belt-tightening reforms, such as direct fees for medical care, and for agreeing to host the US missile shield facility.

The poor result for the Civic Democrats, just a week after they lost a regional election, was expected to further weaken the premier.

Analysts said that Topolanek's opponents within the party, led by Prague mayor Pavel Bem and backed by the president, were likely to attack their leader.

"I will have to decide whether I will run and defend the post of the (party) leader at the (party) congress," Topolanek said on Czech Television.

Meanwhile, Social Democratic leader Jiri Paroubek called the Senate election result "a brilliant, phenomenal success".

He said the government should resign and an early election should be called together with the European Parliament polls in June. (dpa)