LISBON (Reuters) - Portugal will appeal to the European Commission over the planned construction by Spain of a nuclear waste storage facility at the Almaraz power plant because it fears cross-border environmental risks, Environment Minister Joao Matos Fernandes said on Thursday.

Matos Fernandes spoke after talks with representatives of the Spanish government, whose announcement on Dec. 29 of the decision to build the storage facility took the Portuguese side by surprise.

"Portugal will request the intervention of Brussels in this case...Once accepted, the issue between neighbouring countries will have to be resolved by the European Commission," Fernandes said in remarks broadcast by Portuguese television after the meeting in Madrid.

Portugal has no nuclear power reactors and the public is generally opposed to the idea and distrustful of Spain's seven nuclear-fuelled power plants.

Almaraz, on the River Tagus, is located just 100 km east of the Portuguese border. The Tagus crosses into central Portugal from Spain and meets the Atlantic Ocean near the capital Lisbon.

The Portuguese government argues that the project to build the facility next to the nuclear power plant did not evaluate potential cross-border impact, which is against European Union rules.

"We are not saying there is necessarily an impact for Portugal, but any potential impacts have to be properly studied, which has not been done," Fernandes said.

The Spanish energy ministry declined to commment on the dispute and the environment ministry had no immediate comment.

(Reporting By Andrei Khalip, additional reporting by Jose Elias Rodriguez, editing by Angus MacSwan)