All 27 EU members must sign up to the Lisbon Treaty for it to go ahead.
Following the no vote in Ireland's referendum last month, EU leaders are desperate to put pressure on the Irish by getting the 26 other countries to approve it.
Poland's parliament gave it the green light in April, but the signature of the country's president, Lech Kaczynski, is essential for the constitution to be enshrined in Polish law.
He was asked whether, following Irish voters' rejection of the treaty, he would ratify it. Mr Kaczynski said: 'This is now pointless.'
And in a sign that he would not be bullied into backing down, he added: 'It is difficult to say how this whole thing will end.
'The bloc functioned, functions and will go on functioning. It's not perfect but such a complicated structure cannot be perfect.'
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