Sweeping U.S. sanctions on Russia's oil industry will make it more expensive for Moscow to sell its oil and complicate sea-borne crude exports due to restrictions on tankers, analysts and traders said on Monday.

The White House, now unconcerned about the effect on gas prices and inflation, blacklisted two of Russia’s biggest oil producers and nearly 200 tanker ships.

Five of those tankers were stationary off Chinese ports and a further seven dropped anchor off Singapore, with others halting near Russia in the Baltic Sea and the Far East, according to Reuters' analysis based on MarineTraffic and LSEG ship tracking data.

Oil-freight derivatives trading surged to the highest in at least a decade as the Biden administration’s sanctions on Russia continued to propel supertanker rates higher.

Oil prices extended gains for a third session on Monday, with Brent rising above $81 a barrel to its highest in more than four months, as wider U.S. sanctions are expected to affect Russian crude exports to top buyers China and India.

Oil prices slipped on Tuesday from the previous day's four-month highs but the market remained supported by continuing focus on the impact of new U.S. sanctions on Russian oil exports to key buyers India and China.

U.S. and global benchmark crude-oil prices settled Monday at their highest since August as investors focused on the potential supply hit from further tightening of U.S. sanctions on Russia’s oil sector.