FORT LAUDERDALE, Fla. (AP) — The U.S. Coast Guard has directed cruise ships to prepare to treat any sick passengers and crew on board while being sequestered “indefinitely” offshore during the coronavirus pandemic.

The new rules outlined in a memo are required for ships in the district that covers Florida, Georgia, South Carolina and Puerto Rico. They also come with a stiff warning: Any foreign-flagged vessels “that loiter beyond U.S. territorial seas” should try first to medically evacuate the very sick to those countries instead.

Many South Florida cruise ships are registered in the Bahamas, where hospital capacity is limited and people are still recovering from last year’s devastating Hurricane Dorian.

The rules, which apply to vessels carrying more than 50 people, were issued in a March 29 safety bulletin signed by Coast Guard Rear Admiral E.C. Jones, head of the seventh district. All ships destined for U.S. ports were already required to provide daily updates on their coronavirus caseload or face civil penalties or criminal prosecution.

Dozens of cruise ships are either lined up at Port Miami and Port Everglades or waiting offshore due to the coronavirus pandemic. Most have only crew aboard, but Carnival Corp., which owns nine cruise lines with a total of 105 ships, notified the SEC on Tuesday that it has more than 6,000 passengers still at sea.

Federal, state and local officials have been negotiating over whether Carnival’s Holland America cruise ships, the Zaandam and Rotterdam, would be allowed to dock at Port Everglades this week. But the company’s Coral Princess is coming, too, with what that ship’s medical center called a higher-than-normal number of people with flu-like symptoms.