By the end of 2024, the U.K. plans to implement electronic travel authorization, requiring visitors who don't need a visa -- including Americans -- to seek permission in advance of travel.
The rule would not apply to British and Irish citizens.
A travel-authorization requirement would "give the U.K. more control of our borders, allowing us to block threats from entering the U.K," said the government, which pointed out that the U.S., Canada, Australia and New Zealand also require electronic travel authorization.
The U.K. envisions that airlines would check and confirm that travelers have the authorization prior to their travel.
The U.K. does not yet have information about the cost. The U.S. charges travelers from Visa Waiver Program countries $21 for electronic travel authorization.