MUMBAI—The Indian government will unveil proposed regulations Monday to create subsidies and expand a "Buy Indian" mandate to give a boost to its lackluster solar-power sector, putting it on a collision course with the U.S.

The new rules will extend local content requirements, which so far have been restricted to a type of technology known as silicon wafers, to thin-film cells as well, Tarun Kapoor, joint secretary in India's Ministry of New and Renewable Energy, told The Wall Street Journal.

...