An investigation by two U.S. senators into the use of H-1B visas by Indian outsourcing companies could negatively influence other outstanding trade issues between the two countries, warned Kamal Nath, India's minister for commerce and industry, on Wednesday.

India has been pushing the United States to ease restrictions on how many skilled professionals can enter the United States. In turn, the United States has been asking India to loosen restrictions in financial services and other sectors. Nath is due to discuss the issues with U.S. Trade Representative Susan Schwab this week in Brussels.

H-1B visas are critical for Indian outsourcing companies, as a significant number of their employees work in the United States. The United States limits the number of those visas it grants to 65,000 a year.

Chuck Grassley, a Republican senator from Iowa, and Richard Durbin, a Democratic senator from Illinois, said earlier this week they've asked nine Indian companies—including top outsourcers Wipro Ltd., Tata Consultancy Services Ltd. and Infosys Technologies Ltd.—for details on their use of H-1B visas. The senators are investigating whether the H-1B program is being used for its intended purpose of filling temporary worker shortages.

"Supporters claim the goal of the H-1B program is to help the American economy by allowing companies to hire needed foreign workers," Durbin said in a statement released Monday. "The reality is that too many H-1B visas are being used to facilitate the outsourcing of American jobs to other countries."