RIYADH (Reuters) — The commander of U.S. Naval Forces Central Command visited Riyadh over the weekend to discuss with the head of Saudi Arabia’s naval forces reinforcing defences against Iranian threats, the command said on Tuesday.

The meeting followed a September 14 drone and missile attack on two Saudi oil facilities that initially knocked out more than 5% of global supply. The United States, European powers and Saudi Arabia blamed the strike on Iran, which denies involvement. Yemen’s Iran-aligned Houthi group has claimed responsibility.

Several countries, including Saudi Arabia, have responded to a U.S. call to form an international maritime coalition to protect commercial shipping in the Strait of Hormuz after attacks earlier this year on several oil tankers in Gulf waters.

Washington and Riyadh have blamed those attacks too on Iran, which it denies. “This visit was an opportunity to discuss our mutual efforts going forward to coordinate defence against provocation and attack”, Malloy said in a statement, citing the importance of regional efforts to counter what it called “Iranian aggression”.

Under Washington’s proposed maritime mission, the United States would provide coordinating ships and lead surveillance efforts while allies would patrol nearby waters and escort commercial vessels with their nation’s flags.

Gulf states, which are big purchasers of Western arms, have invested more in air and land capabilities than in naval assets, and have little experience of coordinating large naval missions.