The United States is “very comfortable and confident in the legal authorities that the president exercised to conduct these strikes,” Kirby said.
Spanish Defence Minister Margarita Robles said Madrid had not joined the military action in the Red Sea because it wanted to promote peace in the region.
“Every country has to give explanations for its actions. Spain will always be committed to peace and dialogue,” she told reporters in Madrid.
Italian Defence Minister Guido Crosetto earlier this week, made clear his reluctance to target the Houthis, telling Reuters that their aggression had to be stopped without triggering a new war in the region.
The diverging opinions in the West over how to tackle the Houthi threat emerged last month when the United States and a number of its allies launched Operation Prosperity Guardian to protect civilian vessels in the busy Red Sea shipping lanes.
Italy, Spain and France did not sign up to the mission, unwilling to put their naval vessels under US command.
All three already participate in an EU anti-piracy operation off the Horn of Africa, and the Spanish defence minister on Friday said the European Union might soon decide on a new initiative.
“The EU could decide … in a few days’ time that there should be a (naval) mission. We do not yet know the scope if that mission is approved, but in the meantime Spain’s position out of a sense of responsibility and commitment to peace is not to intervene in the Red Sea,” she said.