"The key channel by which secondary tariffs on buyers of Russian energy could impact the global economy would be through the level of energy prices," says Kieran Tompkins from the consultancy Capital Economics. If the tariffs work, they will cut the flow of Russian oil and gas to global markets.

President Donald Trump suggested he would impose increased tariffs on additional countries buying energy from Russia — including China — after saying earlier Tuesday that he would raise levies on Indian exports within 24 hours.