The US State Department has strengthened its travel warning against the UK to ‘Level Four: Do Not Travel’ because of Covid-19.

This is the highest travel advisory rating, warning US citizens not to travel to the UK.

The State Department’s website reads: “The Centers for Disease Control and Prevention (CDC) has issued a Level 4 Travel Health Notice for the United Kingdom due to Covid-19, indicating a very high level of Covid-19 in the country.”

The CDC warns: “Travelers should avoid all travel to the United Kingdom. Because of the current situation in the United Kingdom even fully vaccinated travelers may be at risk for getting and spreading Covid-19 variants and should avoid all travel to the United Kingdom.

“If you must travel to the United Kingdom, get fully vaccinated before travel.”

The State Department has also reclassified more than 100 other countries as ‘Level Four: Do Not Travel’.

China and Japan remain at ‘Level Three: Reconsider Travel’.

Earlier this week, the State Department said it would add more than 100 countries to its Do Not Travel list, as Covid-19 “continues to pose unprecedented risks to travellers” and it “strongly recommends US citizens reconsider all travel abroad”.

MoreUK-US travel ‘not a question of if, but when’

US to ‘significantly’ increase countries on its ‘Do Not Travel’ list

The move has dented optimism for the introduction of a UK-US travel corridor when the UK government intends to allow non-essential overseas travel next month.

The UK is expected to confirm its “green” list of countries in early May under a new traffic light system.

The US had been tipped to be one of the few places Britons can visit without the need to quarantine on return, but there has not been any official confirmation.

On Tuesday, UK transport secretary Grant Shapps confirmed he is having “regular” talks with his opposite number in the US, Pete Buttigieg, about transatlantic travel.

Keith Glatz, international vice-president at Airlines for America (A4A), said “it’s not a question of if, but a question of when” the ban on UK visitors is lifted.