US president also says any country that trades with Iran will ‘face tremendous economic consequences’.US President Donald Trump has again threatened Iran with unprecedented economic action, accusing Tehran of failing to seize an opportunity to reach a deal as talks aimed at ending the more than five-month conflict between the two countries remain deadlocked.In a post on Truth Social on Wednesday, Trump announced what he called the “most crushing economic operation ever taken against any country” against Iran, using his signature all-caps style.Recommended Stories list of 4 itemslist 1 of 4USS Lincoln woes highlight US Navy limits in prolonged Iran war: Expertslist 2 of 4Iran’s hardline parliament raises concerns with ‘foreign infiltration’ planlist 3 of 4North Korea leader’s sister denies talks with ‘hostile’ USlist 4 of 4US pressure on Israel needed for peace in Syriaend of listHe said Iran had “failed to take” the opportunity to make a deal and would face “economic warfare and isolation on an unprecedented scale”.Trump also threatened sanctions against any country that does business with Iran.“ANY country that allows its financial institutions, businesses, airports, or government entities to provide any type of lifeline to Iran will itself face TREMENDOUS Economic Consequences. Oil smuggling, swap lines, cash transfers, exchange houses, ship registries, front companies — it all needs to stop NOW. You know who you are. This will be an ECONOMIC D-DAY, and we need all of our Allies to stand with the United States of America to isolate, and defeat, the Iran threat,” he wrote.This is not the first time that Trump has threatened Iran with economic sanctions.His administration has waged a pressure campaign against Iran since April under the banner of Operation Economic Fury, designed to isolate Tehran and block its revenue streams.The US has already imposed sweeping sanctions on Iran’s oil, shipping and financial sectors, seeking to cut off the revenue Tehran earns from energy exports. It has also imposed a naval blockade on Iranian ports and targeted companies, brokers and tankers accused of helping Iran sell its oil abroad.‘Frustration’Al Jazeera’s Mike Hanna, reporting from Washington, DC, said Trump’s latest post showed “a degree of frustration”.“I think the first question is: What economic pressures can he exert on Iran that are not already being exerted?” he said, adding that there was no clear answer because Trump had given no indication of what measures he planned to take.“Is this, to the Iranians, another shouting threat? Well, on the surface, that is the case. But perhaps his target audience is an American public that continues to oppose this ongoing conflict. He is now taking what he hopes will be seen in the public forum as a very strong stance, regardless of the fact that we do not have specific details on which to judge the possible efficacy of this particular move to strengthen economic action against Iran,” Hanna said.Analysts said Trump could target China, as well as Iraq and Turkiye with secondary sanctions.In China, “he can target the financial institutions that provide services to the independent teapot refineries. Those are the refineries that are the last group still purchasing Iranian oil,” said Nader Habibi, a Middle East economics professor at Brandeis University.“The challenge is that the Chinese government has warned Chinese entities not to cooperate with US sanctions. Given that trade negotiations are under way between the United States and China, it will be interesting to see how China reacts if, in the next few days, the United States announces specific targets or institutions that cooperate with those teapot refineries,” he said.Habibi added that it would also be difficult for the US to fully enforce restrictions on Iran’s overland trade with Turkey, Iraq and Central Asia.“It is only an avenue for achieving full enforcement of sanctions along those borders, with the cooperation of the respective governments.”