The launch of a travel corridor between Hong Kong and Singapore has been postponed for two weeks amid a surge of Covid-19 cases in Hong Kong.
The deal was due to kick in on Sunday, allowing passengers to fly both ways without the need to self-isolate.
The decision is a blow to attempts by the two financial hubs to revive their battered travel sectors.
Hong Kong reported 43 new infections on Saturday, the highest daily toll in nearly three months.
The number includes 13 cases with unknown transmission sources, raising fears the local outbreak could get out of control.
"Today's decision is a responsible decision," Hong Kong Commerce Secretary Edward Yau told reporters. "For any scheme to be successful, it must fulfil the conditions of securing public health and also making sure that both sides [are] comfortable and feel safe about the scheme."
The decision will be revisited in early December, he added.
Under the travel bubble arrangement, travellers would be required to take a Covid-19 test before departure and upon arrival. There would be no restrictions on the purpose of travel but passengers would have to take designated flights, and a maximum of 200 people would be allowed to travel each way per day.
Neither Hong Kong nor Singapore has seen the large outbreaks of the virus experienced elsewhere. With small populations and heavy dependence on international air travel, they hope the travel corridor will help their key tourism and aviation sectors amid a global downturn.
Shukor Yusof, an analyst with aviation consultancy Endau Analytics, said the travel arrangements were fraught with challenges.
"There is no solution until the vaccine is available to all. The more airlines swim against the Covid tide, and try to beat the odds, the worse it will become. Best to endure, stay put, refine the business model and conserve cash," he told AFP news agency.
Last month, an air travel corridor was introduced between Australia and New Zealand in which New Zealanders are exempt from self-isolation requirements when arriving in the state of New South Wales and the Northern Territory.
The International Air Transport Association (IATA), which represents 290 airlines, expects traffic this year to be 66% below the level it was in 2019. The IATA estimates that it will be at least 2024 before air traffic reaches pre-pandemic levels.
According to the World Travel and Tourism Council, the pandemic led to a 72% drop in international tourists in the first half of the year. However, there has been a rebound in domestic tourism in some markets, such as China.