The Foreign Office today advised against all but essential travel to the US.
The change in travel advice follows the US government extending its transatlantic flight ban from 26 European countries to include the UK.
The US restrictions will be enforced from the early hours of March 17 in response to the coronavirus pandemic.
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The FCO said: “From 23:59 eastern daylight time on 16 March (03:59 GMT 17 March) it will not be possible for many British nationals to enter the USA.
“We therefore advise against all but essential travel to the US, due to the travel restrictions.”
British travellers in the US will be allowed to leave.
But the FCO added: “The new US travel restrictions are likely to affect commercial flight schedules to the UK and we recommend that British travellers who wish to leave by air make appropriate arrangements to ensure their travel plans can be met.”
The US is the fourth most popular destination for UK travellers, with 3.47 million visitors travelling there last year.
The FCO’s advisory follows similar measures advising against all but essential travel to Spain, the UK’s number one outbound destination.
Sri Lanka guidance
The Foreign Office has also updated it’s travel advice for Sri Lanka, advising against all but essential travel to the destination.
In updated guidelines, the FCO said: “The Sri Lankan Government has decided that people arriving from the UK, or having travelled through the UK, will not be allowed to enter Sri Lanka from midnight (1830 GMT) on March 16.
“We therefore advise against all but essential travel if you are travelling from or via the UK.”