He said he would be open to reforms to Medicare, but he didn't spell out any details. Lew also said he would work with the committee on a rewrite of the tax code.
Beyond the budget, Lew is expected to hew closely to the positions Geithner struck on Europe's debt crisis, the U.S. relationship with China and the administration's defense of the Dodd-Frank financial overhaul law that the banking industry has fought to weaken.
Some Republicans voted against Lew because they were not satisfied with his answers about his previous employment with Citigroup, including a brief time when he was chief operating officer for an investment unit in 2008. The unit has been criticized for making risky investments that imploded during the financial crisis. And Lew received a bonus of nearly $1 million in early 2009, a time when Citi was being bailed out by taxpayers.
Lew told the panel that he didn't make decisions about the investments being offered to clients. He said his bonus reflected compensation for his work.
Sen. Charles Grassley, R-Iowa, opposed Lew's nomination. He cited questions about his time at Citi, as well as Lew's compensation while working as chief operating officer at New York University.
"Mr. Lew's eagerness and skill in obtaining bonuses, severance payments, housing allowances and other perks raises concerns about whether he appreciates who pays the bills," Grassley said.
One potential weakness for Lew: His relative inexperience with financial markets and international economic crises â¿¿ areas that had played to Geithner's background. Analysts think Lew will keep pressuring Europe to deal aggressively with its budget and debt issues. But they think this will consume less of his time given that Europe's debt crisis now poses less of a threat to the global economy.
On trade, Lew is expected to keep prodding China. The U.S. trade gap with the world's second-largest economy hit another record high last year. No breakthrough is expected, though.