WASHINGTON (REUTERS) - President Barack Obama is expected to nominate a former State Department official, Richard Verma, to be the new U.S. ambassador to India, just ahead of a visit to Washington this month by new Indian Prime Minister Narendra Modi, a congressional source said on Thursday.

Verma, an Indian-American, served as assistant secretary of state for legislative affairs at the State Department in the Obama administration from 2009 to 2011.

He is currently a senior counselor at the Steptoe & Johnson law firm and the Albright Stonebridge Group, a business advisory company led by former Secretary of State Madeleine Albright.

The Congressional source, who spoke on condition of anonymity, said the nomination was expected to be confirmed by the White House on Thursday.

If his nomination is confirmed by Congress, Verma will replace Nancy Powell, who resigned in March after a damaging dispute over the treatment of a junior Indian diplomat, Devyani Khobragade.

Khobragade was arrested and strip-searched in New York last year, an incident that took the US-India relationship to its lowest ebb in a decade.

The US Embassy in New Delhi is currently headed by a charge d'affaires, Kathleen Stephens.

Modi is due to visit Washington on Sept 29-30 for a trip aimed at revitalising ties.

He was denied a visa to the United States in 2005 after Hindu mobs killed more than 1,000 people, most of them Muslims, in 2002 while he was chief minister of his home state of Gujarat.