President Barack Obama plans to change tax policy in a move that is likely to be unpopular with corporations that have international divisions and for individuals who use tax havens. President Obama vowed to "detect and pursue" American tax evaders today as he announced a plan to close tax loopholes and clamp down on overseas shelters. The president said he wants to prevent U.S. companies from deferring tax payments by keeping profits in foreign countries rather than recording them at home. He also called for more transparency in American bank accounts that are held in tax havens such as the Cayman Islands.