The Spanish government has closed its airspace to U.S. planes conducting missions against Iran and is also denying Washington access to its military bases, the defense minister said Monday.

"The bases are not authorized, and of course neither is the use of Spanish airspace for actions related to the war in Iran," Margarita Robles told journalists, confirming a report by the Spanish daily, El Pais.

Spain's refusal to cooperate has "complicated" U.S. military operations by forcing bombers to change their routes and logistics on their way to the Middle East, El Pais reported.

The transit or landing of planes is allowed only in case of an emergency, the newspaper said.

Spanish Prime Minister Pedro Sanchez has emerged as the highest-profile Western leader to consistently oppose the war, launched by U.S.-Israeli strikes on Feb. 28 and which has since engulfed the entire Middle East.

His stance has infuriated Spain's traditional NATO ally, with U.S. President Donald Trump threatening to cut trade ties in their latest policy clash.

Spain had already sparked Trump's anger by refusing to agree to raise NATO defense spending to 5% of member states' GDP as demanded by the U.S. president.