Warsaw  - Polish President Lech Kaczynski will ratify the Lisbon Treaty on Sunday evening, presidential aide Aleksander Szczyglo told TVN24 on Thursday.

"The president keeps his word," Szczyglo told the news broadcaster. "He announced many times that if the Irish say 'Yes' in a second referendum, then his decision will be positive and the ratification process will be finalized."

Kaczynski had pledged to sign the treaty soon after it got the nod from Irish voters. His advisers sent mixed signals immediately after the vote, however, saying there was no need for haste.

The delay was a possible bid to negotiate a better position for Poland in the EU, reports said.

After Kaczynski's signature, Czech President Vaclav Klaus will be the sole European leader who has yet to ratify the treaty, which must first get approval from the Czech Republic's Constitutional Court.

The treaty needs unanimous approval from the 27-member bloc before it can be implemented. (dpa)