Marie and Ed Graham greet daughter-in-law Nicola Graham and son Ally as they meet granddaughter Iona, 1, for the first time after arriving from London as the US reopens air and land borders to coronavirus disease (COVID-19) vaccinated travellers for the first time since the COVID-19 restrictions were imposed, at Sea-Tac Airport in Seattle, Washington, U.S. November 8, 2021. REUTERS/Lindsey Wasson

Concerns over the omicron coronavirus variant and fresh travel restrictions have led to a spike in hotel booking cancellations globally, online hotel search firm Trivago said on Tuesday, threatening to upend a fragile recovery in global tourism.

Cancellation rates increased to 35 percent since November and holiday travel planning was down 10 percent, the company said, adding that most travelers were choosing domestic destinations.

The company did not say what the cancellation rates were prior to November.

The omicron outbreak, first reported in southern Africa, has led to a flurry of new testing rules and border closings, raising concerns ahead of the important Christmas travel season.

Multiple events ranging from sports and trade shows to corporate parties have been canceled, also leading to a slowdown in hotel bookings.

Private Label Manufacturing Association has canceled its annual trade show, which was scheduled to take place in Chicago in February next year, due to uncertainty sparked by the new variant.

US investment bank Jefferies on Wednesday canceled client parties and virtually all but essential travel after nearly 40 new COVID-19 cases were reported at the firm.

Trivago said overall activity around holiday travel planning has slowed, growing by just 4 percent since the variant was discovered. By comparison, Christmas travel increased by 34.7 percent in the same one-to-two-week period in 2019.

Last month, the company said it saw an increase of 35 percent in search traffic in the week leading up to Thanksgiving.

US travellers are sticking with Las Vegas and New York as top holiday destinations, the company said.

"Much like 2020, domestic travel is the preferred option as consumers look to reunite with friends and family," Trivago said.

International flight searches from the United States were down between 35% and 39 percent in the first week of December, according to rival Booking Holdings Inc`s travel website Kayak.

They were down about 25 percent just before Thanksgiving, a day before the World Health Organisation named the new COVID-19 variant and said it may spread more quickly than other forms, according to Kayak.

Fears over the variant have grown after British Prime Minister Boris Johnson warned of a "tidal wave" of new cases, with the country reporting the first publicly confirmed death in the world due to omicron on Monday.