Pakistan, Sept. 19 -- India has spent the past four years defending its purchases of Russian oil as an exercise in national interest. Cheap crude helped contain the import bill, shield consumers from some of the fallout of the Ukraine war and allowed New Delhi to insist that its foreign policy would not be written in Washington. That argument is now facing its most difficult test.

The US Congress has passed legislation giving President Donald Trump authority to impose tariffs of up to 100 per cent on major buyers of Russian energy. India is squarely in the frame. The measure has not yet translated into a 100 per cent tariff, and much will depend on how Trump chooses to use the powers Congress has handed him. The threat alone, however, ha...