P&O Cruises has extended its pause in operations until November 12th.
At the same time, the Carnival Corporation-owned line has cancelled two long itineraries due to depart in January.
A Caribbean and South America cruise onboard Aurora has been cancelled, along with an around the world trip on Arcadia.
The line blamed the decision on advice from the Foreign & Commonwealth Office warning against overseas cruise trips.
P&O Cruises president, Paul Ludlow, said: “It is clear that while the guidance is in place it is not advisable for us to resume operations.
“Given long-term planning, combined with the complexity and length of these long-haul itineraries and evolving border restrictions, we need to ensure that we adhere to the guidance as it stands.
“I know that these January cruises, in particular, are holidays of a lifetime and we are so sorry for the disappointment that these cancellations will cause.”
Guests booked on the cancelled cruises will automatically receive an enhanced 125 per cent future cruise credit or alternatively can fill in the website form for a refund.
At the same time, Seabourn announced today that it will cancel upcoming voyages for three cruise ships in its fleet as a part of its pause in global operations.
The announcement applies to Seabourn Encore, which will not sail again before November 5th, and Seabourn Ovation, which is out of action until December 20th.
Seabourn Sojourn will also pause operations until May 24th next year.
The Carnival-owned brand had previously announced a pause in its global operations until November 20th.
The decision to cancel additional voyages is a proactive action to deal with the circumstances continuing to evolve from the global response to the Covid-19 situation, the line said.
“We have been saying for some time that our resumption of service will come gradually, and this action reflects that discussion.
“The health, safety and well-being of our guests, crew and the people in destinations we visit remain a top priority,” said Josh Leibowitz, president of Seabourn.
“Like many who watch the travel industry, we are encouraged by the signs emerging around the world that point to travel’s progress toward return.
“When our expert science and medical advisors and our destinations support the ability to resume travel on Seabourn, we’ll be ready.”
In some good news for the sector, however, Costa Cruises is planning to restart its operations from Italian ports gradually on September 6th.
The decision follows the approval from the Italian government for the resumption of cruises – which will also see Aida return to operations.
The first ship to set sail will be Costa Deliziosa, on September 6th, offering weekly cruises from Trieste to discover the most beautiful destinations in Greece.
She will be followed by Costa Diadema, on September 19th, operating seven-day cruises in western Mediterranean from Genoa to experience the best of Italy and Malta.
Further details on potential Costa Deliziosa and Costa Diadema itineraries will be announced in the coming days, with a number of sailings expected in September.
However, all other vessels will remain in port until at least the end of next month.