Carnival PLC (LON:CCL) said it has cancelled its July sailings for all US operations except for three ships based in Florida and Texas.
If Carnival can find a way to be allowed to visit Alaska, another ship based in Seattle might also sail, it added.
"The company is cancelling sailings on all other ships through July 30, 2021.
Guests whose cruises are cancelled are eligible for a future cruise credit (FCC) and onboard credit (OBC) or a full refund, said the statement.
Christine Duffy, president of Carnival Cruise Line, added: "We continue to have constructive discussions with the CDC but still have many questions that remain unanswered.
We are working diligently to resume sailing in the U.S. and meet the CDC guidelines," she said.
"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."
Late week, the Carnival Splendor based in Sydney, Australia, cancelled sailings from Aug. 19 to Sept. 17, 2021.