NEW DELHI - Sonia Gandhi, India's ruling Congress party head and the country's most powerful politician, has undergone surgery in the United States for an undisclosed medical condition, the party's spokesman said on Thursday.

Gandhi could be away for two to three weeks.

"She has undergone surgery and her condition is satisfactory," Janardhan Dwivedi, who is the party's general secretary, told reporters in a surprise announcement.

The 64-year-old Gandhi is the leading figure in a family dynasty that has ruled the country for much of India's independence. She nominated Prime Minister Manmohan Singh in 2004 and is widely considered to be more powerful than him.

A four member panel, including her son Rahul who is widely seen as the prime minister-in-waiting, has been appointed to run political affairs in her absence.

Her absence and uncertainty over the effect of her illness could further cloud the Congress party has it deals with a host of corruption scandals and high inflation.