DUBAI/WASHINGTON (Reuters) - Joe Biden plans to scrap what he calls the “dangerous failure” of President Donald Trump’s maximum pressure policy on Iran should he win the U.S. election, but after years of confrontation his diplomacy-first approach to a historic Middle East foe could prove an unforgiving challenge.Vice president under President Barack Obama when Iran’s 2015 nuclear deal with six powers was struck, Biden has pledged that if Tehran resumes compliance with the pact he will return to the agreement, which Trump quit in 2018, reimposing sanctions. With Iran’s economy crippled, its ties with Washington have been at boiling point ever since, and an international consensus over Iran’s nuclear work -- which the West suspected was aimed at creating a nuclear bomb -- has been in disarray. The pressure on Iran’s leaders to escape from sanctions is severe. Their core support comes from poorer Iranians struggling to survive as the price of bread, cooking oil and other staples has soared and the rial currency has plummeted. The coronavirus has only compounded the pressure. The Iranian media regularly report layoffs and strikes by workers who have not been paid for months. But among the obstacles facing Biden, a Democrat, in his bid to reopen a pathway to detente are Iran’s mistrust of Washington, which deepened sharply when Trump tore up the deal. “Why should we trust Biden? He is like Obama. You cannot trust Democrats,” said a hardline official close to the office of Supreme Leader Ayatollah Ali Khamenei, adding Trump might eventually offer a better deal than the abandoned 2015 accord. Both Trump and Biden have yet to detail how they plan to persuade Iran to go along with their respective approaches. The U.S. Treasury Department on Monday slapped counterterrorism sanctions on key players in Iran’s oil sector for supporting the Quds Force, the elite paramilitary arm of the Islamic Revolutionary Guard Corps.