MADRID (Reuters) - Spain will vote against the European Union’s draft Brexit deal on Sunday unless it is modified to make clear that the future of the disputed British territory of Gibraltar relies on talks between Madrid and London, Prime Minister Pedro Sanchez said.

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Spain’s demands on Gibraltar are the latest push by EU states to obtain more on national interests ahead of Sunday’s summit of EU leaders, but diplomats said there was little concern these would scupper prospects for a deal.

“As of today, if there are no changes with respect to Gibraltar, Spain will vote no to the agreement on Brexit,” Sanchez said during a conference in Madrid on Tuesday.

According to EU rules, the withdrawal treaty is adopted by qualified majority and not unanimity. So a single state like Spain cannot block it. The EU’s executive said it was aware of Spain’s concerns and it expected the issue to be resolved.

A small peninsula on Spain’s southern coast and a British territory since 1713, Gibraltar is a major point of contention in Anglo-Spanish relations. Spain has long claimed sovereignty over it.

Gibraltar is due to leave the European Union along with the United Kingdom in March, although 96 percent of its population voted in the 2016 referendum to remain in the bloc.

SUNDAY SUMMIT

While Spain last week initially welcomed a protocol on Gibraltar in the draft Brexit agreement, Foreign Minister Josep Borrell on Monday said there was confusion over Gibraltar in the main body of the agreement.

That needed to be clarified in the broader political declaration on the new relationship between the EU and the UK, Borrell said. Sanchez reinforced that message on Tuesday.

“If on Sunday in the @EUCouncil the Brexit deal does not recognise that Gibraltar’s situation must be negotiated directly between Spain and the United Kingdom, this government will not accept it,” Sanchez said on Twitter.

“If this government, which is a pro-European government, finds itself in this situation, this means that someone in Brussels didn’t do their work well,” he said, adding that Spain had offered various drafting options both to Britain and to EU negotiator Michel Barnier.

In Brussels, EU spokesman Margaritis Schinas said the bloc agreed last year that “after the UK leaves the Union, no agreement between the EU and the UK may apply to the territory of Gibraltar without the agreement between Kingdom of Spain and the United Kingdom”.

Diplomats in Brussels expected the issue to be resolved by adding more such language in the withdrawal agreement and the declaration on post-Brexit ties between the EU and Britain by Sunday, when they are due to be presented to EU leaders for approval.

Gibraltar borders the Andalusia region where regional elections key for Sanchez’s socialist party as well as his main opponents are held on Dec. 2. Several thousands Spaniards cross the border every day to jobs in the territory.

Gibraltar’s Chief Minister Fabian Picardo on Monday issued a statement regretting the Spanish position.

“It does not come as a surprise that Madrid should seek to raise new Gibraltar issues at the last minute on our negotiations to leave the EU. Raising issue at the 11th hour is a well-known tactic that has been used by Spain in the past while were in the EU,” Picardo said.