MADRID, July 17, 2008 (AFP) - Spain's Constitutional Court Thursday blocked a plan by authorities in the northern Basque Country to hold a referendum on self-determination for the region.

The court unanimously upheld a move by the Madrid government to suspend the referendum, which the Basque parliament approved by a narrow majority on June 27.

Madrid approached the court on Tuesday after the parliamentary approval became law in the region by being published in the official journal, saying the vote planned for October 25 was illegal.

The court now has five months to consider whether the referendum conforms with the 1978 constitution.

The head of the Basque government, Juan Jose Ibarretxe, proposed the move to declare the right of self-determination for the Basque people, a demand of the armed separatist group ETA that is blamed for the deaths of 823 people in its 40-year campaign for an independent Basque homeland.

Ibarretxe first announced the plan, the first part of a proposed 'road map' for new political relations between the Basque region and Madrid, after ETA formally called off a 15-month-old ceasefire in June 2007.

It would ask voters two questions:

1: 'Do you support a process aimed at negotiating an end to violence if ETA first demonstrates, unequivocally, its will to definitively end violence?'

2: 'Do you agree that Basque political parties should begin a process of negotiation to reach an agreement on a democratic accord on the Basque people's exercise of the right of self-determination and that this accord be submitted to a (regional) referendum before the end of 2010?'

Spain's Socialist Prime Minister Jose Luis Rodriguez Zapatero has said he would be open to granting more autonomy to the affluent region, which already enjoys a high level of self-government, as long as this respected the constitution and was the result of a broad agreement on the part of Basque political parties.