Ferguson, who was vice chairman of the Federal Reserve's Board of Governors from 1999 to 2006, is among several Treasury secretary candidates.

The GAO estimated that 21 percent of taxpayers would owe money under the new law, versus 18 percent under the prior law, because of changes in the way withholding is calculated.

The budget deal Senate leaders reached late Wednesday would add nearly $300 billion in government spending over two years and push the deficit higher, exactly the opposite of what the economic textbooks say lawmakers should be doing, said a Moodys economist.

The White House plan to work on tax reform is to start hearings and a markup of the bill after Labor Day.