Voters go to the polls Sunday in Spain's Basque region in an election shaping up as a referendum on the ruling party's push for greater autonomy.

Experts say a big win by the Basque Nationalist Party of Basque president Juan Jose Ibarretxe may set the stage for a showdown with Madrid over his plan for a "free association" with Spain.

Mr. Ibarretxe is at odds with Spanish Prime Minister Jose Luis Rodriguez, who has called the plan a mistake that would divide the Basque people from the rest of Spain.

Also, an obscure communist party is set to win up to a dozen seats in the 75-member parliament following a 2003 decision by Spain's Supreme Court banning the political wing of the Basque separatist group ETA (Batsuna) from running in the election.

Leaders of the ETA terrorist movement have thrown their support behind the little-known party.

Some information for this report provided by AP, AFP and Reuters.