Czech Prime Minister Mirek Topolanek suggested Wednesday that his party might reject ratification of the EU's reforming Lisbon Treaty if parliament failed to approve a US anti-missile base in the country.

The scenario was "possibly one of the cards in play," Topolanek told Czech public radio.

"It is very difficult to imagine that if ratification of the agreement with the US does not go through, that deputies, for example Civic Democrat senators, would vote for the Lisbon Treaty," Topolanek said.

He personally did not consider it acceptable to link the two issues, he added.

Topolanek's Civic Democratic Party firmly backs hosting US radar, part of a wider anti-missile system that Washington says would protect the US and its allies against attacks from "rogue" states such as Iran.

US Secretary of State Condoleezza Rice signed the main radar agreement with her Czech counterpart on Tuesday.

But the Prime Minister's fragile coalition is not sure of winning a parliamentary vote for the anti-missile project.

Members of the junior coalition party, the Greens, have spoken out against it and lawmakers from the third coalition party, the Christian Democrats, are also cool towards it.

On the other hand, a significant number of Civic Democrats share the same eurosceptic views about the Lisbon Treaty as the party's founder and current head of state, President Vaclav Klaus.

The Greens and Christian Democrats are EU enthusiasts.

Ratification of the troubled Lisbon Treaty is currently stalled in the Czech Republic until the constitutional court gives its verdict on whether it clashes with local law.

Klaus has already said he regards the treaty as finished following Irish voters' rejection of it in a referendum last month.