BERLIN (AFP) -- Spain is prepared to compromise to find an institutional treaty for the European Union but expects Poland to do the same, Prime Minister Jose Luis Rodriguez Zapatero said after talks here on Friday.

"Spain is ready to have a more flexible position so that we can make progress," Zapatero said after a meeting with German Chancellor Angela Merkel ahead of next week's crucial EU summit in Brussels.

Zapatero warned that isolation was not an option for Poland, which is bitterly opposed to proposed changes to the voting mechanism for the 27-country bloc.

"The message that I wish to send to our Polish friends is that we need to look ahead. I am sure that no country wants to stay on the sidelines and that no country will stay on the sidelines," Zapatero said.

He was the first of a host of EU leaders to hold discussions with Merkel over a three-day period as Germany -- which currently holds the EU presidency -- seeks to remove obstacles to its goal of putting the bloc on the road towards a new treaty to replace the rejected draft constitution.