The agency had earlier projected a growth rate of 5.7 per cent during the 2020 calendar.
Asia-Pacific economic growth in 2020 will be more than halve to less than 3 per cent as the "global economy enters a recession", S&P said in a statement.
An enormous first-quarter shock in China, shutdowns across the US and Europe, and local virus transmission guarantees a deep recession across Asia-Pacific, said Shaun Roache, chief Asia-Pacific economist at S&P Global Ratings.
"We lower our forecasts for China, India, and Japan for 2020 to 2.9 per cent, 5.2 per cent and -1.2 per cent (from 4.8 per cent, 5.7 per cent, and -0.4 per cent previously)," S&P said.
On Tuesday, Moody's Investors Service had lowered India's economic growth forecast for 2020 to 5.3 per cent (from 5.4 per cent), in the wake of the coronavirus impact on the economy.