The revision comes within days of it flagging concerns over low per capita income and high fiscal deficit. It also comes just two days ahead of the Budget.
"India should be the Asia-Pacific region's bright spot," S&P said and revised steeply upwards its growth estimates.
The rating agency said economic growth will rise to 7.9 per cent in FY 2016, up from its previous estimate of 6.2 per cent, and will go up further to 8.2 per cent in FY 2017 as against 6.6 per cent estimated previously.
It may be noted that the government had earlier this month changed the methodology of computing GDP, which showed a dramatic increase in GDP growth to 6.9 per cent from the earlier 5 per cent in FY2014, and 7.4 per cent for this fiscal, up from a projected 6 per cent.
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In a brief note sent to the press by the rating agency, it is unclear if Standard & Poor's is re-pegging its estimates based on the revisions in GDP computation or not.
"Weaker growth in China and Japan may be weighing on the overall sentiment, although India's star is rising," it said.
Finance Minister Arun Jaitley is slated to present his first full Budget on Saturday, in which the government spells out it growth target for the next fiscal.
The agency had earlier this week come up with a commentary flagging concerns over the fiscal deficit and low per capita income.
"India's low income levels and weak fiscal and debt indicators constrain the country's credit profile," it had said this Monday.