LONDON (AP) — Simplified international travel rules took effect Monday in the U.K., easing quarantine and testing requirements for fully vaccinated travelers from more than 50 countries, and the Conservative government vowed it will seek to regularly expand the rules to more nations.

Still, the rules have sparked anger from many nations in the developing world, particularly India, which have been excluded from the list of countries whose vaccination programs are accepted by U.K. authorities. The New Delhi government on Friday said British citizens traveling in India would have to undergo COVID-19 tests and 10 days of quarantine, similar to the measures imposed on Indian residents visiting the U.K.

As part of the new regime, Britain eased entry requirements for fully vaccinated travelers from 18 countries, including Canada, Japan and the United Arab Emirates. It builds on a pilot phase with U.S. and most European countries that began over the summer.

The Department for Transport said it would take a "phased approach'' to recognizing vaccines administered by additional countries and territories.

"The U.K. government is continuing to work with international partners as we seek to more regularly expand the policy to further countries and territories,'' the department said.

Under the new rules, Britain scrapped its traffic light system for international travel, which applied different rules to travelers from countries in three different categories of COVID-19 risk. Now there are just two categories: a "red list," which bars most non-essential travel, and the rest of the world.

But travelers from non-red list countries aren't all treated equally.

Those who have been fully vaccinated with one of four authorized vaccines and have a certificate from a recognized public health agency are now allowed to enter the U.K. without a negative pre-departure COVID-19 test and without being required to quarantine on arrival.

But travelers coming from countries whose vaccination programs aren't recognized by U.K. authorities will still be required to show a pre-departure test and quarantine for 10 days.

Most countries in Africa and South America, as well as major Asian nations such as China, India and Vietnam, don't have vaccination programs that are authorized by the U.K.

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