WASHINGTON — Jacob Lew, President Obama’s nominee for Treasury secretary, pledged to work with Congress on a comprehensive overhaul of the tax code while urging lawmakers to avoid automatic spending cuts that could slow the economy’s progress.

During a three-hour confirmation hearing Wednesday, Lew fielded a broad range of questions about how he would handle a number of challenging issues, including Europe’s debt crisis, US-China relations, and the implementation of the 2010 financial regulatory overhaul.