WASHINGTON - The US. military launched cruise missile strikes on three coastal radar sites in Houthi-controlled areas of Yemen, retaliating after failed missile attacks this week on a US Navy destroyer, US officials said on Wednesday.The strikes authorized by President Barack Obama represent Washington's first direct military action against Houthi-controlled targets in Yemen's conflict. The Pentagon said initial US assessments indicated the radar sites were destroyed."These limited self-defense strikes were conducted to protect our personnel, our ships, and our freedom of navigation in this important maritime passageway," Pentagon spokesman Peter Cook said. "The United States will respond to any further threat to our ships and commercial traffic, as appropriate."