Mumbai, Sept. 2 -- First Solar, America's largest solar panel manufacturer, has sent a warning letter to India's Waaree Energies, alleging infringement of its patented process to manufacture solar cells, a person aware of the matter said.

The US company has alleged that Waaree's TOPCon cells, which is the most popular solar cell technology today, violate two of its patents. It has asked the company to either stop manufacturing these cells or license the technology from it. First Solar has threatened legal action if Waaree doesn't comply with its warning.

The dispute threatens to disrupt Waaree's lucrative exports business to the US. The company has nearly Rs.30,000 crore worth of export orders, mostly to the US, as per its latest invest...