HONG KONG (AP) — Singapore and Hong Kong on Saturday postponed the start of an air travel bubble meant to boost tourism for both cities, citing a spike in infections in the Chinese territory as a “sober reminder” of risks to public health.

The travel bubble, originally slated to begin Sunday, will be delayed by at least two weeks, Hong Kong’s minister of commerce and economic development, Edward Yau, said at a news conference.

The arrangement is meant to allow travelers between the two cities to enter without quarantine as long as they complete coronavirus tests before and after arriving at their destinations, and fly on designated flights.

Hong Kong reported 43 new coronavirus cases on Saturday, including 13 untraceable local infections.

“For any scheme to be successful, they must fulfill the condition of securing public health, and also make sure that both sides would be comfortable and feel safe about the scheme,” Yau said. “In light of the situation in Hong Kong, I think it’s the responsible way to put this back for a while, and then sort of relaunch it at a suitable juncture.”

Under the initial agreement, the travel bubble was to be suspended if the number of untraceable local infections in either Singapore or Hong Kong exceeded five on a seven-day moving average. The current average in Hong Kong is nearly four, prompting Yau and Singapore's transport minister, Ong Ye Kung, to postpone the inaugural flight.

On Friday, Hong Kong's top health official said that the city had “probably entered” a new wave of cases. Recent clusters have spanned taxi drivers, a dance studio and hotels.

Hong Kong has confirmed a total of 5,561 cases, including 108 deaths. Singapore has reported 58,148 cases, but only 28 fatalities.

Prior to the postponement, Singapore said Saturday morning that travelers arriving from Hong Kong via the bubble would be required to take a coronavirus test on arrival. Originally, only people landing in Hong Kong were to be required to be tested.

Ong said in a Facebook post that the postponement is a “sober reminder that the COVID-19 virus is still with us."

“I can fully understand the disappointment and frustration of travellers who have planned their trips. But we think it is better to defer from a public health standpoint,” he wrote.