The US campaign to tighten pressure on Iran's financial links around the world may face a major limit in China, Tehran's biggest trading partner and leading buyer of its oil. The issue has come up as President Donald Trump prepares to host Chinese President Xi Jinping next month while trying to keep a fragile trade truce between the two countries intact.advertisementRead Full StoryTreasury Secretary Scott Bessent this week announced "Operation Economic Outcast", but did not spell out how the Trump administration would act against China. That has raised doubts over how effective the new push can be when Washington is…