WASHINGTON (BLOOMBERG) - Talks are under way between the United States and China on possible changes to the Chinese government's new aircraft-cleaning requirements that prompted a Delta Air Lines flight to turn back to Seattle and that could trigger the cancellation of some flights to the Asian nation.

The discussions were confirmed on Tuesday (Dec 28) by a State Department official who spoke on condition of anonymity.

The new sanitation mandates - spurred by the spread of Covid-19 - significantly extend the time planes are on the ground and largely copy steps that US airlines already take to clean between flights, representatives for the industry said. There also is a shortage of available workers to carry out the added steps, they said.

The new requirements are part of the changes that countries and industries are making to try to slow the spread of the highly contagious Omicron coronavirus variant.

China has been stepping up border restrictions because of Delta variant outbreaks and detection of the new strain among foreign travellers ahead of the Beijing Winter Olympics in early February.

Hong Kong will mandate a three-day hotel quarantine for air cargo crews to thwart transmission of Omicron.

The US is seeking changes to the new Chinese cleaning mandates, since rigorous disinfecting procedures already are performed between flights by carriers globally, the State Department official said. Airlines implemented extensive onboard cleaning protocols early in the pandemic.

Delta's service to China "remains very fluid" as it evaluates the change in procedures that caused it to turn around a Dec 21 flight to Shanghai, returning the plane to where it took off in Seattle.

The carrier is assessing its twice-weekly trips from Detroit and Seattle to Shanghai on a flight-by-flight basis, a spokesman said on Tuesday.

United Airlines said it is working to comply with the mandate that was put in place last week and has not cancelled any of its four weekly flights between San Francisco and Shanghai.

American Airlines' twice-weekly flight between Dallas-Fort Worth and Shanghai also is affected, the carrier said, without providing further details.

Airlines for America, the lobbying group for major US carriers, declined to comment. The new rules apply to any airline flying into China.

In Asia, ANA Holdings has delayed departure times for flights out of Shanghai and Guangzhou since Dec 22 to allow for the time it takes to clean its planes, a spokesman for the Japanese carrier said.

Japan Airlines' passenger flights to and from China are operating normally, although inbound air cargo into the country has been restricted, according to a spokesman.

US carriers flying from the states stop first in another city, like Incheon or Seoul, South Korea, and change crews before going on to China.

The procedure ensures that flight crews do not surpass the legal number of hours they can work and allows them to avoid an overnight stay that could trigger additional Covid-19 protocol requirements for the aircraft or crew, airline representatives said.

Delta's Flight 287 returned to Seattle after the carrier learnt of the change in cleaning requirements midflight, the Atlanta-based carrier has said. In addition to the time required, the new procedures "are not operationally viable", Delta said.

It wasn't immediately clear what sanitation procedures authorities in China recently put in place.

A spokesman for Shanghai's airport declined to comment earlier. A spokesman for the Civil Aviation Administration of China referred to a Covid-19 control protocol issued in September.