The agreement between Prague and Washington, which was officially approved by the Czech government on May 21, is expected be ratified by the end of 2008.
The document will be put forward for ratification to parliament together with a second agreement on deployment terms and conditions for U.S. service personal, which should be ready by early July when U.S. Secretary of State Condoleezza Rice is due to visit Prague to sign the documents.
Spokeswoman Ivona Novomestskà also said the opposition was preparing a protest rally in the center of Prague upon Rice's arrival on July 9-10.
Around two-thirds of the Czech population are against the radar plans, according to an April opinion poll.
There is also considerable opposition to the deployment plan in the Czech parliament, with the leading opposition force, the Social Democratic Party, demanding a public discussion on the issue.
Russia sees the proposed Central European shield as a potential threat to national security, and believes it would destroy the strategic balance of forces in Europe.