Tourism arrivals around the world are not expected to return to their pre-pandemic levels until 2024 at the earliest, the World Tourism Organization said Tuesday.

The highly contagious Omicron variant, though mild, will "disrupt the recovery" in early 2022 after last year saw four percent growth over 2020, according to the Madrid-based UN agency's World Tourism Barometer.

Tourism revenue in 2020 was 72 per cent down on the previous year -- which closed with the onset of the coronavirus pandemic.

"The pace of recovery remains slow and uneven across world regions due to varying degrees of mobility restrictions, vaccination rates and traveller confidence," the UNWTO said in a press release.

In Europe and the Americas, foreign visitor arrivals surged by 19 per cent and 17 per cent, respectively, last year over 2020.

In the Middle East, however, arrivals declined by 24 per cent in 2021, while in the Asia-Pacific region they were 65 per cent below 2020 levels, and 94 per cent down on pre-pandemic levels.

The statement said tourism professionals "see better prospects" for this year after turbulence in the early months because of the Omicron wave.

The agency predicts a 30 to 78 per cent rise in international arrivals this year over 2021, while remaining far below 2019 levels.

Most experts say they do not foresee a return to pre-pandemic levels until at least 2024, it said.

Many countries are highly dependent on tourism and are eagerly awaiting a return to normal.

"The economic contribution of tourism in 2021 (measured in tourism direct gross domestic product) is estimated at $1.9 trillion (1.68 trillion euros), above the $1.6 trillion in 2020, but still well below the pre-pandemic value of $3.5 trillion," the statement noted.