Washington  - President-elect Barack Obama's pick for treasury secretary could face tough questions in his confirmation hearing after problems arose Tuesday with his taxes and the immigration status of his former housekeeper.

Timothy Geithner, who now heads the Federal Reserve Bank of New York, apparently briefly employed a housekeeper whose immigration papers had expired while she worked for him, the Wall Street Journal reported, citing people familiar with the matter.

She later got a green card and worked legally, but the employment of illegal immigrants has proved a major stumbling block for past government appointees.

Geithner also failed to pay Social Security and Medicare taxes for himself while working for the International Monetary Fund under a complicated tax status that required him to pay the taxes himself that are normally withheld from workers' paychecks by their employers.

He paid the taxes once the matter was brought to his attention, the Journal reported.

Senators were meeting Tuesday afternoon to discuss the issues, but the Obama transition team appeared to think the problems were not major.

Spokesman Robert Gibbs called the problems "honest mistakes" that had been addressed.

"He made a common mistake on his taxes, and was unaware that his part-time housekeeper's work authorization expired for the last three months of her employment. We hope that the Senate will confirm him with strong bipartisan support so that he can begin the important work of the country," Gibbs said in a statement. (dpa)