WASHINGTON — White House chief of staff Denis McDonough and other senior advisers knew in late April that an impending report was likely to say the IRS had inappropriately targeted conservative groups, President Barack Obama's spokesman disclosed Monday, expanding the circle of top officials who knew of the audit beyond those named earlier.

But McDonough and the other advisers did not tell Obama, leaving him to learn about the politically perilous results of the internal investigation from news reports nearly three weeks later, officials said.

The decision to keep the president in the dark underscores the White House's cautious legal approach to controversies, as well as an apparent desire by top advisers to distance Obama from troubles threatening his administration.