The launch of the much-anticipated travel bubble to facilitate leisure travel between Singapore and Hong Kong has been further delayed amid a rising number of Covid-19 cases in Hong Kong.

The Civil Aviation Authority of Singapore (CAAS) said yesterday that both cities have decided to defer the start of the air travel bubble to beyond this month, as the number of local unlinked cases in Hong Kong is still high.

The exact start date of the arrangement will be reviewed late this month.

"Passengers are advised to contact their airlines regarding their travel plans. The Singapore and Hong Kong authorities have been in close discussion and will update when there are further developments," said CAAS.

The move follows harsher social distancing measures to curb what the Hong Kong health authorities warned could be the city's worst Covid-19 wave so far.

Chief Executive Carrie Lam told residents yesterday that the next two weeks will be critical, as she urged residents to stay at home.

The city has been recording more than 70 new daily Covid-19 infections for over a week. Its total tally has crossed 6,300 cases, including 109 deaths.

Meanwhile, the seven-day moving average of unlinked local Covid-19 cases rose to 16 as at Monday. Singapore and Hong Kong had previously agreed that the travel bubble arrangement would be suspended if the number exceeded five in either city.

The bubble would have allowed travellers to fly between the cities with no restrictions on the purpose of travel. Travellers would have to take Covid-19 tests instead of serving quarantine.

The first air travel bubble flight was originally planned for Nov 22, but both governments announced on Nov 21 that it would be delayed.

They said at the time that they would review the situation by early this month.

Singapore Airlines, which was due to operate air travel bubble flights, said it supported the delay.

It said affected customers can rebook their flights or request a full refund.

Ms Alicia Seah, director of public relations and communications at Dynasty Travel, said the agency had received several bookings for tour packages to Hong Kong for the mid-December to Christmas period.

While acknowledging that the delay is unfortunate, she added: "It's really (about) putting the health and safety of travellers as the top priority.

"We understand that the relevant authorities need to prevent the further spread of infection while maintaining economic and social activities in a carefully planned and measured way."

Another travel agency, Chan Brothers, said that since most customers had been adopting a wait-and-see approach towards the air travel bubble, the deferments have not made a big difference to bookings and cancellations.

"We recognise that the situation is a rapidly evolving one, and the baggage of uncertainty that these travel bubbles come with may discourage at least some travellers," said Chan Brothers.

"However, travel bubbles can be a cautiously optimistic first step to a post-pandemic future... a successful implementation can instil confidence for others in discussion, as well as spark similar future dialogues with prospective destinations."