"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.
And with less supply, prices could go up, just as they did when Russia launched its full-scale invasion of Ukraine in 2022. That led to a spike in inflation around the world. President Trump says he isn't worried because of record US oil production.
Mr Tompkins points out that, this time, there are also other reasons to suggest the impact on prices would not be as marked.
He explains that "the current backdrop is one where Opec+ [the group of major oil producing countries and its allies] have significant spare capacity to draw upon".