British citizens are now able to travel internationally to a limited number of destinations as coronavirus pandemic restriction begin to ease furter in the United Kingdom. However, Prime Minister Boris Johnson is warnings that the COVID variant first discovered in India may derail the nation's progress against its outbreak.

Starting this week, citizens from most parts of the U.K. can travel to 12 countries on the nation's "green list" without having to quarantine on their return. This is a massive change for the country since non-essential international has been banned for months as the nation sought to control its once surging outbreak.

While the United States is on the U.K.'s "amber list," meaning people should not travel there due to public health and safety concerns and will have to quarantine before and after arriving to England, Britons can travel to countries like Australia, Iceland, New Zealand and Singapore with only a negative COVID-19 test.

In addition to easing international travel restrictions, the U.K. is relaxing local public health restrictions including allowing up to two households meet indoors, groups of 30 to meet outdoors, and social-distancing rules being dropped. Moreover, the nation has reopened pubs, bars and restaurants for indoor service, as well as allowing indoor entertainment centers like cinemas, theaters, museums and sport stadiums to reopen with capacity limits.

Johnson on Monday assured citizens that the easing of more coronavirus restrictions must be take "with a heavy dose of caution," as the government is still concerned with the new highly transmissible COVID strain first discovered in India, Bloomberg reports. To better combat the India variant, the nation has moved to increase its vaccination rollout to Britons aged 35 and over to help contain the virus and support the National Health Service (NHS).

"We are keeping the spread of the variant first identified in India under close observation and taking swift action where infection rates are rising," Johnson said in a statement on Monday, quoted by Bloomberg. "The current data does not indicate unsustainable pressure on the NHS and our extraordinary vaccination program will accelerate--with second doses being brought forward to give the most vulnerable maximum protection."

The U.K. plans to enter its final stage of easing coronavirus restriction on June 21, but that end date depends on the nation's current outbreak at that time, with Johnson urging citizens to take precautions to keep the spread of the India variant under control.