Tata Motors and Nissan Motor India, besides automobile industry body SIAM, on Tuesday welcomed the Government's move to deregulate diesel prices in the country."This is a long-awaited measure and I am extremely happy that the Prime Minister has seized the opportunity of deregulating diesel price at a time hen crude prices have fallen resulting in a reduction in diesel price due to the deregulation," SIAM President Vikram Kirloskar said in a statement.