LONDON (AP) — The European Union recommended Tuesday that all 27 member countries should discourage all nonessential travel to and from the United Kingdom until further notice.

With EU countries imposing ad-hoc restrictions on U.K. travel following the emergence of a new coronavirus variant, the European Commission urged them to take a coordinated approach, but not prevent people in the U.K. or Europe from returning to their homes.

EU Justice Commissioner Didier Reynders said “member states should take coordinated action to discourage nonessential travel between the U.K. and the EU. At the same time, blanket travel bans should not prevent thousands of EU and U.K. citizens from returning to their homes.”

The EU’s executive arm said people returning to their home countries or main place of residence should be able to do so provided they produce a negative test or quarantine themselves.

Transport workers should be exempt from any travel ban when they are traveling across a border to and from a vessel, vehicle, or aircraft. Essential medical staff should be able to move freely without quarantine provided that they have tested negative within 72 hours of travel.

More than 1,500 trucks snaked along a major highway Tuesday in southeast England near the country’s vital Channel ports or crowded into a disused airport, illustrating the scale of Britain’s isolation after countries from Canada to India banned flights from the U.K. and France barred the entry of its trucks for 48 hours beginning Sunday night.

For a country of islands that relies heavily on its commercial links with France, that’s potentially very serious — and raised concerns of food shortages if the restrictions weren’t lifted by Wednesday.

Home Secretary Priti Patel told BBC radio that the British government is “speaking constantly” with France to get freight moving again. France has said it wants to lift the ban as soon as possible and is looking at ways of testing drivers on their arrival.

“It’s in both our interests, both countries to ensure that we have flow, and of course there are European hauliers right now who want to be going home,” she said.

While the French ban does not prevent trucks from entering Britain, many vehicles that carry cargo from the country to the continent return laden with goods. The fear is that will fall off — reducing deliveries to Britain at a time of year when the U.K. produces very little of its food and relies heavily on produce brought from Europe by truck.

Also, some drivers or their employers might decide against entering Britain for fear they won’t be able to get back home.

The restrictions were creating a feeling of isolation in Britain akin to what the residents of Hubei province in China at the start of the year or those in northern Italy must have experienced a few months later.

Given that around 10,000 trucks pass through the Dover every day, accounting for about 20% of the country’s trade in goods, retailers are getting increasingly concerned if there is no resolution soon.

Andrew Opie, director of food and sustainability at the British Retail Consortium, warned of potential shortages of food like lettuce, vegetables and fresh fruit after Christmas if the borders are not “running pretty much freely” from Wednesday.

The problem, he explained, is the empty trucks sitting in England can’t get pick up new deliveries for Britain.

“They need to get back to places like Spain to pick up the next consignment of raspberries and strawberries, and they need to get back within the next day or so, otherwise we will see disruption,” he said.

Over the weekend, British Prime Minister Boris Johnson imposed strict lockdown measures in London and neighboring areas amid mounting concerns over the new variant to the virus, which early indications show might be 70% more transmissible.

As a result, Johnson scrapped a planned relaxation of rules over Christmastime for millions of people and banned indoor mixing of households. Only essential travel will be permitted.

Amid questions about whether vaccines being rolled out now would work against the new strain, the chief executive of BioNTech — the German pharmaceutical company behind one of those shots — said he was confident it would be effective, but further studies are need to be completely sure.

Ugur Sahin said Tuesday that “we don’t know at the moment if our vaccine is also able to provide protection against this new variant” but because the proteins on the variant are 99% the same as the prevailing strains BioNTech has “scientific confidence” in the vaccine.

There are mounting concerns that the whole of the U.K. will be put into a national lockdown after Christmas as new infections soar, including in Wales where 90 soldiers from the British Army will be reenlisted to drive vehicles from Wednesday to support health teams responding to emergency calls.

The British government’s chief scientific adviser, Patrick Vallance, warned Monday that measures “may need to be increased in some places, in due course, not reduced.” For many, that was code for another national lockdown.

While the new variant is being assessed, countries were trying to limit contact with Britain, even though there is evidence of the strain elsewhere already.

In Switzerland, for example, authorities are trying to track an estimated 10,000 people who have arrived by plane from Britain since Dec. 14 — and has ordered them to quarantine for 10 days.

Switzerland was one of the 40-odd countries to ban flights from the U.K. over concerns about the new variant.

The quarantine order is likely to affect thousands of Brits who may have already headed to Swiss ski resorts. Unlike many of its neighbors, Switzerland has left most of its slopes open, attracting enthusiasts from around Europe.

The virus is blamed for 1.7 million deaths worldwide, including about 68,000 in Britain, the second-highest death toll in Europe, behind Italy’s 69,000.

The chaos at the border comes at a time of huge uncertainty for Britain, less than two weeks before it completes its exit from the EU and frees itself from the bloc’s rules. Talks on a post-Brexit trade relationship between the two sides are deadlocked.