WASHINGTON (AP) — President Joe Biden said Thursday the U.S. would immediately begin turning away Cubans, Haitians and Nicaraguans who cross the border from Mexico illegally, his boldest move yet to confront the arrivals of migrants that have spiraled since he took office two years ago.

The new rules expand on an existing effort to stop Venezuelans attempting to enter the U.S., which began in October and led to a dramatic drop in Venezuelans coming to the southern border. Together, they represent a major change to immigration rules that will stand even if the Supreme Court ends a Trump-era pub...