President Barack Obama will ask Congress on Friday for authority to close the Commerce Department and create a new export agency, an overhaul that could save $3 billion and help inoculate him against Republican election-year charges that he is a big-government liberal. White House budget official Jeffrey Zients told reporters the reorganization would fold together the Office of the U.S. Trade Representative and other trade bodies now spread across Washington, giving businesses a single point of contact and ensuring federal spending goes further to boost exports.