The panel would come up with an interim report soon and the final ruling is expected only around first week of October, the official added.
As per the norms, India will give its views and comments on the the interim report and it is up to the panel to include those views.
"The ruling, if it goes against India, will have implications for the domestic solar sector," the official said adding Canada has lost a similar case at the WTO.
The US had alleged that India's programme appears to discriminate against US solar equipment by requiring solar energy producers to use locally manufactured cells and by offering subsidies to those developers who use domestic equipment.
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It is also alleged that forced localisation requirements restrict US exports to India markets.
On January 11, 2010, India launched its national solar policy -- the Jawaharlal Nehru National Solar Mission. India had earlier set a target of generating 20,000 megawatts of solar power by 2022 which has been increased five fold to one lakh MW.