The US embassy in Jordan warned its citizens on Wednesday against travelling to the port city of Aqaba, citing an "imminent" threat.
The American warning says "credible information has been received regarding a possible imminent threat in the Gulf of Aqaba region."
"The US Embassy recommends that all non-official and personal travel to Aqaba be deferred for at least the next 48 hours," the statement said without elaborating.
Last month, the US Embassy in Tel Aviv told American citizens travelling to the Israeli Red Sea resort of Eilat that they needed to know where the nearest bomb shelter was.
The warning angered the Israeli government which said that the alert should apply to next door Aqaba.
Rockets from Egypt's Sinai, where Islamist militants have operated in the past, hit Israel's and Jordan's Red Sea ports on Aug. 2, killing a Jordanian civilian and injuring three others. Israeli officials said Hamas was behind the attacks.
Al-Qaeda has been active in Jordan and has carried out attacks there in the past.