Coca-Cola and PepsiCo have been under fire since the New Delhi-based Center for Science and Environment said 11 of their drinks contained average pesticide levels that are 24 times higher than limits agreed by India's government.

"This kind of action is a setback for the Indian economy," said undersecretary for International Trade Franklin Lavin, "In a time when India is working hard to attract and retain foreign investment, it would be unfortunate if the discussion were dominated by those who did not want to treat foreign companies fairly."

"I'm hoping that (US) companies don't use this as a measure to decide whether to invest in India," said Kiran Pasricha, the US head of the Confederation of Indian Industry (CII).

The soft-drinks giants have hit back with a barrage of press statements and publicity campaigns in India to insist that their beverages are perfectly safe.

Coke and Pepsi account for nearly four-fifths of India's two-billion-dollar soft-drinks market.

The U.S. is India's largest investment partner, with a 17 percent share. India's total inflow of U.S. direct investment topped one billon dollars last year, according to U.S. government data.