PARIS, May 26 : European stock indexes gave up some recent gains on Tuesday and oil prices rose after new U.S. strikes in southern Iran dampened investors' hopes that a U.S.-Iran peace deal could be imminent. Market sentiment had turned more positive over the past week as traders bet on a de-escalation in the U.S.-Israel war on Iran, which has severely disrupted Middle East oil and gas supplies since it began in late February. But they readjusted this view on Tuesday after the U.S. said on