Oil prices tumbled on Thursday on reports that the United States is considering tapping its reserves to combat a supply crisis sparked by the Ukraine war. However, equities struggled to build on the week’s rally after Russia poured cold water on hopes that ceasefire talks were progressing, leaving the prospect of a protracted war in eastern Europe that has already sent shockwaves through the world economy. West Texas Intermediate tumbled more than five per cent and Brent North Sea crude more than four per cent as reports said President Joe Biden was looking at releasing a million barrels a day for several months as he tries to temper a surge in the market to more than $100. Concerns about demand in China owing to a lockdown in Shanghai was adding to downward pressure. The White House this month put an embargo on oil from Russia as part of a series of wide-ranging sanctions against the country for its invasion. However, that sent prices soaring further and put added upward pressure on world inflation, which was already at multi-decade highs. Officials said the president would make a statement on Thursday on plans to cut energy costs “and lower gas prices at the pump for American...