European Union leaders agreed to acknowledge that the Czech Republic faced constitutional hurdles in ratifying the bloc's troubled Lisbon Treaty, rejected last week by Ireland, diplomats said.

"The European Council noted that the parliaments in 19 member states have ratified the treaty and that the ratification process continues in other countries," the leaders agreed in a summit declaration, one of the diplomats said.

"(The European Council) noted that the Czech Republic cannot complete the ratification until the Constitutional Court delivers its positive opinion" on the treaty, the diplomat quoted their statement as saying.