President Joe Biden has ordered a halt to asylum processing at the U.S. border with Mexico when illegal entries reach a threshold deemed excessive. The measure takes effect immediately because the new policy is triggered when arrests for illegal entry reach 2,500. About 4,000 people already are entering the U.S. each day. It's a major policy shift on a critical election-year issue that’s exposed Biden to Republican criticism over an unprecedented surge in new arrivals in an election year. Advocates say the new measure will put migrants in danger and violate international obligations to provide safe haven to people whose lives are threatened. The Biden administration denies that. Legal challenges are imminent.