With signs pointing to a big return of tourists to Greece in July during the lingering COVID-19 pandemic, June has been slow and now hit with the news that the United Kingdom said residents who travel to the hot spot would face quarantine when they come home.

The UK has kept Greece, Spain, Portugal and other popular destinations on an “amber list,” of countries declared not fully safe to visit, taking a shot at the European Union after leaving the bloc earlier this year.

That led to a mass cancellation of British tourist bookings for Greece for June with many travel sites hoping to lure people offering no-charge cessation of reservations because of the uncertainty.

The UK might revise its listings as soon as June 7 for Greece although the next more complete ratings aren't due until June 28, which means, if approved, Greece would have a big leg up on its tourism rivals.

Britain, along with Germany, is the most important market for Greek tourism: In 2019 Greece attracted 3.5 million British tourists and another 1 million in 2020, the paper said, and they spent 2.5 billion euros ($3.04 billion) in a record-busting 2019, the Bank of Greece reported. It fell to 749 million euros ($911.27 million) in 2020 when the pandemic raged and international travel was limited severely.

The UK will rank itself as amber as well, meaning Brits on vacation abroad are scrambling to get back to avoid quarantine, seeing airline tickets jump as much as 500 percent from Portugal, said Kathimerini.

The Jet2 airline has canceled all its international flights and holiday packages up to July 1, while TUI UK canceled its holiday packages from Britain to Greece and Spain until mid-June, adding to the worry about a tourism hit.

But Ryanair CEO Michael O’Leary said he's not among the anxious and that despite the news that will cut into June bookings hard he said he believes it will ease in July as more countries speed vaccinations for vacations.

But easyJet had to cancel more than 500 flights scheduled for Portugal while Akis Skertsos, the top deputy to Prime Minister Kyriakos Mitsotakis, said Greece was prepared for the eventuality that's likely to be temporary.

He said that opening to tourists on May 15, those who are vaccinated, have a negative test or have recovered from the Coronavirus, was a pilot test to see how it would work although optimism had been building over expected bookings.

While Greece, which been accelerating its vaccination campaign called Eleftheria (Freedom) after a slow start caused by a cumbersome European Union distribution program, it has also altered the process of reporting COVID cases to meet UK requirements to try to get onto the “green list,” of cleared countries.