Prague - A US-Czech deal to place an anti-missile radar in the former East Bloc nation sparked resistance Friday among a junior governing party that may hold the key to the plan's parliamentary approval.

The Greens have warned that they will approve the US project only if it is clear that it will become part of NATO anti-missile defences in the future.

Prime Minister Mirek Topolanek's centre-right government has a slim lower-house majority and the six Green lawmakers could be crucial.

NATO leaders agreed Thursday at a summit in Bucharest "to explore ways" of integrating the planned US missile shield in Czech Republic and Poland "with any future NATO-wide missile defence architecture."

Some Greens in the Czech parliament said the clause is too vague.

"It is a positive shift, but it is impossible to talk about an integration of the radar into a NATO command at the moment. It is possible that we will vote against it," Czech Education Minister and Greens vice-chairman Ondrej Liska told Czech television.

The Greens are split over the issue. The party's leader, Vice-Premier Martin Bursik, and Foreign Minister Karel Schwarzenberg, who was nominated by the Greens, support the Czech-US deal and are satisfied with the NATO declaration.

The left-leaning opposition opposes the project and wants a referendum.

US plans also call for Poland to host 10 interceptor missiles for the missile shield, which Washington says is aimed against so-called rogue states such as Iran. Russia has opposed the plan.

Czech and US officials announced Thursday that they completed talks on the main diplomatic treaty on placing a radar for planned US missile defence system on Czech soil.