Iran's top negotiator warned of a faster, heavier and more painful response to US attacks as renewed fighting between the two countries continued into its sixth month. Parliament speaker Mohammad Bagher Ghalibaf said Americans must understand before it is too late that the rules of the game have changed. The warning followed Washington's announcement that it had struck Iranian oil tankers after Tehran attacked American warships in regional waters. Iranian state media also said the Navy attacked a US remote-controlled vessel attempting to enter the Strait of Hormuz, a crucial oil and gas shipping chokepoint, but the US military called the report a total lie. US Defence Secretary Pete Hegseth threatened to destroy and sink Iranian oil tankers if Iran attacks US ships. The conflict resumed last Sunday after a 60-day ceasefire formally expired last month, with strikes and retaliation reported in Iran, the United Arab Emirates, Bahrain, Kuwait and Jordan. Months of negotiations have not produced lasting peace, while the strait has remained effectively closed since the war began. US Energy Secretary Chris Wright said 9 million barrels of oil a day were passing through the waterway and that flows were probably two-thirds or more of pre-conflict levels. US diesel prices reached $5.85 a gallon on Friday, compared with $3.71 a year earlier, adding pressure on Donald Trump ahead of the November midterm elections.