U.S. President Donald Trump has announced additional 25% tariff on India for its purchases of Russian oil, bringing the combined tariffs imposed by the United States on its ally to 50%.

India is likely to be among the countries worst hit by U.S. President Donald Trump's trade offensive, with tariffs on Indian imports set to surge to 50% if a deal is not struck in three weeks.

On Wednesday, Donald Trump doubled US tariffs on India to 50%, up from 25%, penalising Delhi for purchasing Russian oil - a move India called "unfair" and "unjustified". The tariffs aim to cut Russia's oil revenues and force Putin into a ceasefire. The new rate will come into effect in 21 days, so on 27 August.