European Union membership candidate Croatia could join the bloc under the Treaty of Nice, which has defined EU institutions since 2003, rather than the still to be ratified Lisbon Treaty, Czech Prime Minister Mirek Topolanek said Monday, according to dpa. "The EU enlargement is not related to the Lisbon Treaty. ... Formally it would be possible to expand the current Nice Treaty by some amendment," he told reporters. French President Nicolas Sarkozy said earlier that EU could not accept new members, including Croatia, before adopting the Lisbon Treaty, aimed at overhauling institutions and simplifying decision- making in the 27-member bloc. While EU leaders signed the treaty in December 2007, its ratification by member states has been complicated after Irish voters rejected it in a June referendum. France - which holds the bloc's six-month rotating presidency until January 1, 2009 when the Czech Republic takes over - is working to rescue the pact. "It is - I don't want to say blackmail - but very strong pressure," Topolanek said of the French efforts. The Czech Republic's upper house of parliament, the Senate, initiated a constitutional review of the treaty and thus suspended its ratification. Unlike President Vaclav Klaus, an outspoken critic of the pact and further ratification, the premier told reporters that he favours its approval, preferably this year. Topolanek said some lawmakers from his Civic Democrats would approve the EU accord in exchange for an opposition nod to the Czech- US missile shield agreements. But he vowed to support both deals. "I will not hamper either one of them," he said.