Carnival Cruise Line says despite constructive talks with US health authorities over a July restart, many questions "remain unanswered".
The line wants to resume sailings onboard three ships from Florida and Texas, with Carnival Vista and Carnival Breeze sailing from Galveston, and Carnival Horizon from Miami.
Additionally, it hopes to deploy Carnival Miracle to Seattle to take on some of Carnival Freedom’s Alaska departures, if a solution can be found to allow sailing to resume in the region.
Carnival said owing to the ongoing uncertainty, guests booked on these sailings are free to cancel without penalty by 31 May and receive a full refund.
The line on Tuesday (12 May) confirmed all planned sailings on its other ships, due to depart up to and on 30 July, have now been cancelled; guests with affected bookings are eligible for its future cruise credit and onboard credit offer, or a full refund.
"We continue to have constructive discussions with the US Centers for Disease Control and Prevention, but still have many questions that remain unanswered," said the line’s president Christine Duffy.
"We are working diligently to resume sailing in the US and meet the CDC guidelines. We sincerely appreciate the continued patience and understanding of our guests and travel advisor partners and will share additional information as quickly as we can."
Carnival has also extended Carnival Splendor’s cruise pause for another month, affecting sailings from Sydney due to depart from 19 August to 17 September.