WASHINGTON — The Trump administration announced Monday it is reactivating economic sanctions on Iranthat were lifted as part of the landmark multinational nuclear accord — a tough move that may nonetheless leave the U.S. more isolated.

The action follows up on President Donald Trump’s unilateral decision in May to withdraw from the 2015 Joint Comprehensive Plan of Action negotiated by the Obama administration to lift sanctions on Iran in exchange for a freeze on its nuclear program.

European nations, Russia and China had urged Trump to stay in the pact. And on Monday, the European Union moved to thwart America’s reimposition of Iran sanctions, announcing a “blocking statute” to shield EU operators to recover damages and ban EU persons from complying with the sanctions.