Lech Kaczynski, Poland’s president, signed the Lisbon treaty reforming the functioning of the European Union Saturday afternoon, leaving his Czech counterpart as the lone holdout who has not yet ratified the pact.

Although Mr Kaczynski and his twin brother Jaroslaw, the former prime minister, had negotiated the treaty, the president ended up worrying that the treaty undercut the power of newer member states and gave too much weight to Germany. Parliament ratified the pact last year, but Mr Kaczynski held off on signing until after the second Irish referendum passed last weekend.

With José Manuel Barroso, the European commission president, Fredrik Reinfeldt, Swedish prime minister, and Jerzy Buzek, the European parliament president, looking on, Mr Kaczynski signed the document in the presidential palace.

Calling the new treaty a change in the quality of the EU, Mr Kaczynski added: “The Union remains a linking of national states, of sovereign states, and it should stay like that.”

Mr Kaczynski’s signature now leaves Vaclav Klaus, the Czech president, as the only impediment to the full ratification of the Lisbon treaty by all 27 EU member states.

Mr Klaus has also worried that Lisbon would undermine Czech sovereignty. Initially he too said he would wait until after the Irish referendum. But in the meantime a group of Czech senators has filed a complaint with the Czech constitutional court, and Mr Klaus has said that he cannot sign until after the court rules.

On Friday, Mr Klaus added a new condition, calling for a Czech opt-out from the pact’s charter of rights and freedoms similar to that obtained by Britain and Poland in order to prevent possible land claims by the descendants of ethnic Germans expelled after the war.

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