What is the 'secondary tariff' imposed by Trump on India?
It is not aimed at magnifying a primary tariff on Russian energy

In a new move of foreign policy, US President Donald Trump has announced the imposition of a "secondary tariff" on imports from India.
This measure, set to take effect in 21 days, adds a punitive 25% levy on top of an existing 25% tariff, with the explicit goal of penalising India for its continued purchase of oil from Russia, reports The Straits Times citing a Bloomberg article.
The concept of a "secondary tariff" is a tool designed to use economic pressure against one country in an attempt to influence the actions of a different country.
This approach is somewhat conceptually similar to that of secondary sanctions, which the US has long used to amplify the impact of its primary sanctions on adversaries.
Secondary sanctions typically target commercial activities involving a sanctioned entity that occur outside of US's legal jurisdiction.
Therefore, by threatening to block access to the US financial system and global dollar transactions, these sanctions compel foreign companies and individuals to cease business with the sanctioned entity or risk losing access to the US market.
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However, the "secondary tariff" on India is distinct.
It is not aimed at magnifying a primary tariff on Russian energy, as the US has had a complete ban on such imports since 2022.
Instead, the additional 25% tariff is designed to compel the Indian government to adopt a similar ban on Russian oil, thereby aligning with the larger US objective of pressuring Russia to end its war.
This is not the first time Trump has introduced such a mechanism.
In March, a similar tariff was created for countries that purchase oil from Venezuela citing 'threats' to US 'national security'.
Bloomberg reports that the US can track such international oil purchases through satellite technology that monitors the identifying transponders on shipping vessels. This technology enables analysts in and out of government to, for example, follow oil tankers loading in Russia and unloading in India.