The signing of a treaty on the deployment of a US missile shield near Prague has been delayed as Czech citizens continue their protest.

Negotiators had been unable to set a date for the official signing, said Czech Foreign Ministry spokeswoman Zuzana Opletalova on Monday.

"We have tried for May 5, but we did not succeed,'' she added without elaborating.

This came amid the announcement of the US embassy in Prague three weeks ago that Secretary of State Condoleezza Rice would travel to the Czech capital in early May to sign the treaty.

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Later on Monday, Prime Minister Mirek Topolanek said the deal could be signed in early June together with a secondary treaty that deals with issues including taxes and the legal status of US soldiers to be deployed to the Czech territory.

Both treaties will need parliamentary approval and negotiations on the second, "complementary'' treaty have not been concluded yet.

The proposed US missile defense system calls for a tracking radar in the Czech Republic and 10intercepotors missile in Poland.

However, the plan has been faced strong objections from the Czech opposition and Russia.

Russia fiercely opposes the plan as a real threat to its security which could trigger a new arms race, rejecting Washington's claims that the system is aimed at protecting against possible attacks from what it calls "rouge states."

Russian Foreign Minister Sergey Lavrov had earlier said that Moscow might protect its security by deploying weapons capable of piercing the US missile shield if Washington doesn't take Moscow's concerns into consideration.

Also Monday, activists protesting the plan penetrated the military area southwest of Prague where the radar is to be built.