Beijing has vowed to retaliate against Washington’s expanded Iran sanctions targeting Chinese entities, threatening a clash that could erode recent stability in the US-China relationship and become a new flashpoint weeks before President Xi Jinping visits the US, according to observers. But they say that efforts on both sides, such as this week’s Track 1.5 dialogue, could serve as a check on tensions and allow each side to understand the other’s concerns. The US on Monday announced fresh...