The Czech government is preparing to sign an agreement in principle over the deployment of part of a US anti-missile shield on its soil in the face of strong public opposition.

The fruit of months of negotiations, the agreement, covering the installation of a tracking radar which would be twinned with an anti-missile silo, probably in neighbouring Poland, should be signed Tuesday at 1300 GMT (3:00 pm local time) by Foreign Minister Karel Schwarzenberg and US Secretary of State Condoleezza Rice.

Anti-base protesters, who have stepped up their actions in recent months with a hunger strike, occupation of the military site earmarked for the US base and marches, have planned two demonstrations in the Czech capital.

Opinion polls show that two-thirds of Czechs are opposed to hosting the US radar. Opposition even strengthened to 68 percent in May according to the results of a survey released by the CVVM agency at the start of July.

Backing for a referendum on the issue is even stronger, at 73 percent, according to the same survey, even though the coalition government has set its face firmly against such a step arguing that parliament should decide.

Right-wing premier Mirek Topolanek, whose pro-US sentiments are as marked as his reserves towards the European Union, proposed Czech participation in the US anti-missile shield as one of the first acts of his newly created coalition government when it was formed in January 2006.

Topolanek has stressed the strategic significance of the step for a country that had already joined the EU and NATO after 40 years in the Soviet bloc which did not end until the fall of the communist regime in 1989.

But he is still far from being certain of winning a parliamentary vote for the radar base.

"This is an important thing for our security, an important thing from the perspective of our membership of the alliance (NATO), I am convinced that responsibility will prevail in the end..." deputy premier and minister for European Affairs, Alexandr Vondra, said Sunday on Czech public television.

But it is "not very likely" that the key parliamentary vote on the radar will take place before the US presidential elections or George W. Bush's departure, the head of the Upper House, Premysl Sobotka, told AFP.

For the opposition Social Democrats, the bilateral radar deal clashes with the Czech Republic's European commitments and the principle of common European defence.

The opposition has also raised questions about what use the radar would be on its own as US-Polish negotiations on the interceptor base falter on Warsaw's demands for the US to guarantee it a permanent anti-missile protection, for example by furnishing it with Patriot missiles.

In addition, Czechs' fears of becoming a target have been fueled by frequent warnings from Moscow, hostile to the radar facility in what used to be its own back yard.

On Sunday, Moscow's man in Prague, ambassador Alexei Fedotov, repeated that the radar has raised "deep unease" in Russia. "Our worries have not been diminished by the answers given (...) everyone is able to imagine that Russia will take adequate steps to safeguard that assure an adequate level of security," he said, adding that he did not want to speculate on whether the measures would be "symmetrical or asymmetrical."

While the main diplomatic deal over the radar, which promises the Czechs priority protection in case of attack, is ready for signature, another two complementary agreements are still stalled as the two sides haggle over the details.

These deals cover the conditions and status of US servicemen at the base and scientific and research cooperation with the US, which Topolanek in March presented as Prague's only real condition.