Washington DC - President Donald Trump threatened Monday to "substantially" hike US tariffs on goods from India over its purchases of Russian oil – a key source of revenue for Moscow's war on Ukraine.

Trump's heightened pressure on India comes after he signaled fresh sanctions on Moscow if it did not make progress by Friday towards a peace deal with Kyiv, more than three years since Russia's invasion.

Moscow is anticipating talks with special envoy Steve Witkoff, who is expected to meet President Vladimir Putin this week.

On Monday, Trump said in a post to his Truth Social platform that India was "buying massive amounts of Russian Oil" and selling it for "big profits."

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"They don't care how many people in Ukraine are being killed by the Russian War Machine," Trump added.

"Because of this, I will be substantially raising the Tariff paid by India to the USA."

But he did not provide details on what tariff level he had in mind.

For now, an existing 10% US tariff on Indian products is expected to rise to 25% come Thursday.

India's foreign ministry said Monday that the US and European Union were "targeting" it due to its buying of Russian oil, adding that the moves were "unjustified" and that it would protect its interests.

"The targeting of India is unjustified and unreasonable," India Foreign Ministry spokesman Randhir Jaiswal said in a statement, after US President Donald Trump vowed to raise tariffs on the country over its oil purchases from Russia.

"Like any major economy, India will take all necessary measures to safeguard its national interests and economic security," he added.