WASHINGTON — The United States on Thursday warned allies and China alike to join President Donald Trump's new campaign to isolate the Iranian economy and "collapse" the government in Tehran. U.S. Treasury Secretary Scott Bessent's comments underscored how Trump is shifting to economic rather than military pressure on Tehran as his unpopular war drags towards the six-month mark. Under pressure at home over the impact of the war and with crucial midterm elections looming, Trump had on Wednesday promised the "most crushing" economic operation ever against Iran. "It is going to work in Iran and we are going to collapse this regime," Bessent told U.S. broadcaster CNBC. Bessent underlined that Washington expects both allies and rivals to join the ramped-up campaign on Iran. "This is going to be the greatest coordinated economic isolation in the history of the world. And we are going to them and saying you are either with us or against us," he added in a message to allies. Asked whether the United States would pressure China, Bessent said that "many conversations are best to have in private," b