Russia has increasingly had to turn to a so-called "ghost fleet" of aging tankers to ship oil and avoid the cap.
Panama, the Republic of the Marshall Islands, and Liberia have allowed some of those ships to carry their flags, according to Lloyd's List Intelligence and oil analysts.
Lloyd's List Intelligence has said nearly 40% of the about 535 dark-fleet tankers have registered ownership via companies incorporated in the Marshall Islands.
It also seeks to give leverage to countries buying oil outside the price-cap coalition to get discounted oil from Russia.
The group is asking Liberia and the Marshall Islands to increase awareness among those in the trade that its flag should not be used for tankers transporting oil priced above the cap.
Persons:
Dado Ruvic, Lindsey Whyte, John Berrigan, Brian Nelson, Timothy Gardner, Simon Webb, Rosalba O'Brien
Organizations:
REUTERS, Rights, Marshall, Intelligence, Britain's Treasury, U.S . Treasury, Reuters, EU, Thomson
Locations:
WASHINGTON, U.S, Liberia, Marshall Islands, Panama, Moscow, Ukraine, Russia, China, India, Republic, Marshall, Washington, British