Spain will not take part in any military mission in the Strait of Hormuz because it considers the U.S.-Israeli war on Iran to be illegal, Madrid's defense and foreign affairs ministers said on Monday.

The leftist coalition government led by Prime Minister Pedro Sanchez has criticized the offensive and banned participating U.S. aircraft from using jointly operated bases in southern Spain. Defense Minister Margarita Robles rejected a demand by President Donald Trump for military support to secure the waterway - which Tehran has de facto blocked to oil tanker traffic - and his threats of a "very bad future" for NATO allies failing to do so.

"Spain will never accept any stopgap measures, because the objective must be for the war to end, and for it to end now," Robles said.

The situation in the strait is a matter of grave concern for Europeans, but the European Union's position should be that the war must end regardless of economic considerations, Foreign Minister Jose Manuel Albares said.

"We mustn't do anything that would add even more tension or cause the situation to escalate further," he told reporters in Brussels.

Some EU members such as Germany, Italy or Greece have also signaled they will not join military operations in the strait, while others including Denmark have yet to make a decision.