Most of the 20,000 U.S. troops requested by the Department of Homeland Security to round up and detain undocumented migrants are expected to be rejected by the Defense Department because of concerns that it could violate the law, according to a U.S. official.

U.S. President Donald Trump's administration has directed immigration officials to largely pause raids on farms, hotels, restaurants and meatpacking plants, according to an internal email reviewed by Reuters,