The prospect of flying combat aircraft from NATO territory into the war zone "raises serious concerns for the entire NATO alliance," the Pentagon said.
Instead, the West has focussed its pressure on sanctions, mainly on individuals and financial institutions. Up until now, oil and natural gas had been excluded.
The United States is not a leading buyer of Russian oil and Europeans, who are far more reliant on it, have been reluctant to follow suit. Britain, however, said it would also phase out the import of Russian oil and oil products by the end of 2022, while the EU published plans to cut its reliance on Russian gas by two thirds this year.