President Barack Obama has tried a lot of ways to get the attention of Syrian President Bashar Assad: International pressure, a “red line,” and assistance to the rebel forces fighting him. On Friday, Obama threw down another card from his deck: gunboat diplomacy.

Starting with targeted leaks and then a murky official statement from Defense Secretary Chuck Hagel, the administration warned Damascus that it has ordered U.S. Navy warships to close their ranges with Syria just in case Obama decides to order an attack.

Obama, by his own account, isn’t there yet. He told CNN earlier in an interview aired Friday that before deciding what to do next, the United Nations must formally conclude that Assad had in fact ordered the chemical weapons attack that is said to have killed hundreds or thousands of people, including women and children.

And even then, the U.S. could only move ahead with some kind of military action if it had the approval of the U.N. or a broad international consensus, Obama said.