"There's no doubt about this, [Omicron] has an extraordinary capability of spreading," Dr Anthony Fauci told NBC's Meet the Press programme on Sunday as quoted by BBC.

Dr Fauci, who advises the US government on the pandemic, said the variant was now "raging through the world".

Several countries in Europe are now tightening measures to prevent the spread of the virus.

Dr Fauci said the rapid spread of Omicron in the US could have a serious impact on health services across the country.

"Our hospitals, if things look like they're looking now, are going to be very stressed," he was quoted by BBC.