Security forces in the Jordanian port of Aqaba are hunting for suspected Arab militants who fired three rockets at two US warships and nearby Israel.
Hundreds of personnel are involved in the hunt
Hundreds of police and troops conducted house-to-house searches for Iraqi, Syrian and Egyptian suspects.
An internet statement, purportedly from a group which claims links to al-Qaeda, said it was behind the attacks.
One rocket hit a warehouse, killing a Jordanian soldier. The others fell near a hospital and Eilat airport in Israel.
The White House denounced the incident.
"We strongly condemn all attacks like these and are investigating in co-operation with Jordanian officials," spokesman Trent Duffy said.
"The US will always make every effort to support and defend our servicemen and women in harm's way, as they protect the American people."
Security forces cordoned off part of Aqaba in their hunt for Friday's attackers, as helicopters flew overhead.
A Jordanian security source said earlier that officers were searching for two Iraqis and a Syrian thought to have rented an industrial warehouse from which the rockets were fired.
Officials say the attackers fired three Katyusha rockets.
One of them whistled over the bows of the USS Ashland and slammed into a warehouse on the quayside of the Red Sea port.
The rocket aimed at Eilat's airport hit a taxi, but caused no injuries.
A statement, allegedly from the Abdullah al-Azzam Brigades, said the attacks were the group's first in Jordan, and were aimed at both the US and Israel.
The group is one of several to have said it carried out the bombings on a market and hotels in the Egyptian resort of Sharm al-Sheikh on 23 July.
Correspondents say Friday's attack is the most serious on a US navy ship since the bombing of the USS Cole in Yemen in 2000 that killed 17 sailors.
Both the USS Ashland and its sister amphibious ship, the USS Kearsarge, left the port in response.
Aqaba is Jordan's only sea port. Eilat is about 15km (9 miles) away, located at the northern end of the Red Sea.