US Secretary of State Condoleezza Rice and her Czech counterpart Karel Schwarzenberg signed yesterday a missile shield treaty despite protests from the Czech public and Russia, and she called it a key treaty of 21st century.

Rice said the signature of the main treaty on the stationing of a US radar base on Czech soil is important not only for the United States and the Czech Republic, but also for NATO and the whole international community.

She emphasized that the threat of a missile attack is not "imaginary" as Iran continues enriching uranium.

The document signed yesterday is a key treaty of the 21st century, she said, adding that it unites friends and allies faced with the same risk.

The planned US radar base on Czech soil will be useful even by itself, Rice said after signing the treaty on the radar with Schwarzenberg.

The US Navy can also protect the Czech Republic and the whole territory with the AEGIS system thanks to the radar base, Rice pointed out.

Schwarzenberg said that the treaty is an expression of the Czech Republic's consistent security policy and that it will promote the security not only of the country, but of Europe and the whole Euro-Atlantic area.

The main treaty still needs to be approved by Czech parliament and President Vaclav Klaus. Negotiations about SOFA agreement that defines legal status of the US soldiers at the planned radar base have not been completed yet.

The United States plans to build a radar base in the Brdy military district, some 90 kilometers southwest of the Czech capital Prague, along with an interceptor missile base in neighboring Poland.

Apart from the radar treaties, the United States and the Czech Republic are also ready to sign an agreement on cooperation in technology and industry.

Czech Prime Minister Mirek Topolanek has said he considers the technical agreement far more important than the radar deal, noting that the United States has similar agreements only with a few countries such as Australia, Britain and Japan.

However, a recent opinion poll showed that up to 70 percent of Czech citizens oppose the project. Several hundred people rallied in Prague's Wenceslas Square late Tuesday to protest against the signature of the radar base treaty.

The demonstrators called on the Czech government to resign. They said Prime Minister Topolanek is a liar and Rice a war criminal.

The opponents called for a referendum on the radar base to be held. They said some 100,000 people have signed a referendum petition.

Russia is also strongly opposed to the missile defense system plan in eastern Europe, saying the plan poses a threat to its strategic interests.

Russia still perceives the US move as a threat to its own security, Russian General Yevgeni Buzhinski said in Lidovy dum, headquarters of the Czech opposition Social Democrats (CSSD), in Prague yesterday.

Buzhinski, who is in charge of negotiations on the issue with the United States, said his country still remains doubtful about the alleged danger which has been used to justify the project.

The United States says the anti-missile system, designed to target threats from countries like Iran, could not possibly pose any danger to Russia considering its nuclear arsenal.

Meanwhile, the US talks with Poland about the anti-missile base have stalled with Warsaw demanding in return billions of US dollars for the modernization of its army.

On her trip to Prague, Rice told journalists that she did not know when the talks with Poland could be closed. She conceded that a long way is yet to be covered, responding to a journalist saying that the anti-missile defense system is still in the stage of development.