(BRUSSELS) - The European Commission on Tuesday reminded Warsaw of its commitment to ratify the EU's troubled Lisbon, after Polish President Lech Kaczynski refused to sign the text already rejected by Irish voters.

"Poland like the other member states has signed the treaty and has committed to ratify it," commission spokesman Pia Ahrenkilde Hansen told reporters in Brussels.

She also recalled that Kaczynski was "a main actor" in the negotiations on the treaty which was agreed by EU leaders in the Portuguese capital Lisbon last December.

Her comments came hours after Kaczynski announced in, an interview published Tuesday, that he will not sign the EU's Lisbon Treaty, saying it was pointless after Irish voters rejected it in a referendum last month.

The Polish parliament voted in April to ratify the charter, a key reform treaty meant to streamline EU decision-making, but it needs the signature of the president to become definitive.

Irish voters rejected the Lisbon Treaty in a referendum held on June 12, putting EU reform plans in jeopardy as it needs to be ratified by all 27 EU member states to enter into force.

Kaczynksi's refusal to ratify the treaty is a serious blow to French President Nicolas Sarkozy, who has set himself the task with finding a way of overcoming the Irish rejection of the treaty.

France took over the six-month rotating EU presidency on Tuesday.

The European commission spokeswoman stressed that the EU leaders had agreed that "the ratification process continues" following the Irish 'no' vote.

Poland's pro-European liberal Prime Minister Donald Tusk had endorsed that opinion, rather than the eurosceptic conservative president Kaczynski.

The Polish hurdle adds to the uncertainty over the future of the Lisbon Treaty which had been scheduled to come into force on January 1, 2009 but must first be ratified by all 27 member states.

The Czech parliament could yet also pose a problem to the ratification process.

Sarkozy has decided to postpone a trip to Ireland to discuss the EU reform treaty to July 21 due to his heavy schedule, his office said Tuesday.

Sarkozy was due to travel to Dublin on July 11, but an aide said the trip would be delayed for "scheduling reasons".

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