While Lew was at Citi, the bank received the first installments of a $45 billion bailout, support that has since been repaid. Lew was paid a $940,000 bonus in early 2009.

Asked about the propriety of such a large bonus at a time when the bank was being bailed out, Lew told the committee that he was compensated for his work and he would leave it to others to judge.

If he is confirmed by the Senate, Lew would be the first Treasury secretary to take the job after being a president's chief of staff since James A. Baker III served as Ronald Reagan's chief of staff before becoming Treasury secretary in 1985.

Beyond the budget, Lew is expected to hew closely to the positions Geithner struck on such issues as 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.

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.

Lew will also need to calm investors who have grown concerned about possible currency wars after Japan's new government sought to lower the value of the yen as a way to boost exports and its weak economy. A weaker yen makes Japanese goods cheaper overseas and foreign goods costlier in Japan.

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