Russia and China vetoed a U.S. resolution at the U.N. Security Council to extend the mandate of experts monitoring Iran's nuclear program. The vote, occurring less than a week before a much-anticipated meeting between President Xi Jinping and President Trump, deepened geopolitical tensions. China's U.N. ambassador Fu Cong urged members to avoid "double standards, political manipulation, pressure and confrontation." Russia's Vasily Nebenzya condemned the "destructive path of our Western colleagues" driven by economic interests. Britain, France, and eight nonpermanent members supported the U.S. measure, but the vetoes created a monitoring gap. Jennifer Locetta, U.S. ambassador to the U.N., called the action "obstructionism" benefiting the Iranian regime. Iranian officials did not immediately address the vote. Complicating matters for the United States, a U.N. fact-finding mission reported "reasonable grounds to believe the United States committed a war crime by launching indiscriminate attacks."

The conflict underscores the distance between world powers over the U.S. pressure campaign on Iran. China and Russia argued the sanctions had expired and the issue should no longer be debated, supporting Tehran's right to a civilian nuclear program. Fu Cong stated U.S. decisions to pull out of the 2015 nuclear agreement and wage war were "at the root of the current crisis." Chinese purchases of Iranian oil have kept Iran's economy afloat. In August, China ordered companies not to comply with aggressive U.S. sanctions. Meanwhile, the International Atomic Energy Agency reported being denied access to Iran's nuclear facilities. The war, beginning with U.S.-Israeli strikes in Iran in late February, has opened a new front in U.S.-China rivalry.

A U.N. fact-finding mission report further escalated tensions, stating it had "reasonable grounds to believe the United States committed a war crime" through indiscriminate attacks. The report cited two U.S. attacks resulting in civilian casualties. This finding adds another layer of complexity to an already fraught diplomatic landscape, highlighting the deepening rift between Washington and its rivals over Iran's nuclear program and broader regional conflicts.