Carnival Cruise Line and P&O Cruises Australia will now resume operations from 2 December, while Princess Cruises is now targeting a 12 December resumption.
The move will affect Carnival Spirit and Carnival Splendor departures, which had previously been placed on pause until 29 October. Guests and agents are being notified.
"Carnival will resume cruising when the time is right and will do so with enhanced health measures developed in conjunction with government authorities, public health experts, local ports of call and the Clia," said the line in a statement.
P&O Cruises Australia said its 2 December extension would affect cruises onboard Pacific Adventure, Pacific Explorer, Pacific Dawn and Pacific Aria.
In a statement, the brand said it would continue to take guidance from authorities, public health experts and "society" to inform its plans to restart sailing.
The line has extended its flexible payment and cancellation policy, P&O Assurance, to the end of the summer season in the region; guests booked on sailings due to depart up to 31 January 2021 can now cancel their booking for any reason up to 48 hours before departure and receive future cruise credit to the value of the fare paid.
President Sture Myrmell said the extension would allow guests to plan ahead, adding it was clear "society is not yet ready to return to sailing". "We will continue to liaise with governments and public health experts as all align on how people should gather and holiday,” said Myrmell.
"We remain hopeful the start of summer will bring new opportunities for the entire travel and tourism industry, which contributes so much to many regional economies around Australia.
"In the meantime, we are trying to provide guests with as much certainty as possible and flexibility around their bookings while we all wait for the day when cruising resumes.”
Princess Cruises, meanwhile, has extended its pause in cruise operations until 12 December, which it said would affect cruises throughout Australia and New Zealand.
The line cited the continued progression of Covid-19 and related decisions of various governments, health authorities and airlines regarding travel restrictions.
Guests who have paid in full for any cancelled voyages will receive a refundable future cruise credit worth 100% of the cruise fare paid as well as a non-refundable bonus equal to 25% of the cruise fare paid.
Alternatively, they can forfeit the bonus and request a full refund, although this must be done by 30 September or they will automatically receive the FCC offer. Travel agent commissions will be protected on bookings paid in full.
