President Donald Trump speaks Thursday at the White House Garden about the U.S. dropping out of the Paris climate change accord.

WASHINGTON — President Donald Trump’s decision to pull out of the landmark Paris climate accord sends an unmistakable message to the world: America First can mean America Alone.

Trump’s move, announced with great fanfare in the White House Rose Garden on Thursday, immediately leaves the United States isolated on a paramount global concern. It demonstrates the U.S. is willing to back away from a coalition it assembled just 18 months ago. Nearly 200 countries joined the landmark deal forged under Trump’s predecessor. Now the U.S. stands with only Syria and Nicaragua as countries on the sidelines. Nicaragua balked because it found the deal’s standards insufficient.

It’s a bitter blow to stalwart European partners who launched an aggressive campaign to convince Trump that American leadership is central to combating climate change. Even a direct appeal from the Vatican wasn’t enough to persuade the president.

Miguel Arias Canete, the European Union’s top climate change official, called Trump’s decision “a sad day for the global community.”

For anxious allies, Trump’s rejection of the Paris pact is particularly jarring in the wake of his first international trip last week. Standing in the heart of Europe, Trump publicly lectured NATO partners about their military commitments and offered no explicit endorsement for the collective defense agreement at the core of trans-Atlantic security for decades. His stunning posture left the distinct impression that for the new American president, the nation’s long-standing obligations to allies are neither unshakable nor unbreakable.

Trump did little to quell those concerns Thursday. Offering a glimpse into his apparent anxiety over how he’s viewed on the world stage, Trump argued that the same countries practically begging him to stay in the Paris accord were in fact mocking the United States’ participation.

“We don’t want other countries laughing at us anymore and they won’t,” Trump declared. “I was elected to represent the citizens of Pittsburgh, not Paris.”

Indeed, Trump’s supporters cheered the decision, which marked the fulfillment both of his campaign promise to scrap the climate accord and his broader pledge to put American interests above all else. As a candidate, he vigorously accused President Barack Obama of capitulating to other nations in negotiations not only on the Paris pact, but also multi-country trade deals and the agreement to curb Iran’s nuclear ambitions.

Trump’s record of holding to those promises is mixed: He moved swiftly to withdraw from the sweeping Pacific Rim trade pact the Obama administration negotiated, but has signaled to other nations that he plans to stay in the nuclear deal so long as Iran lives up to its obligations.

To be sure, Trump is hardly the first American president to turn his back on a predecessor’s international agreement. President George W. Bush provoked similar anger from European allies when he decided not to implement the 1997 Kyoto climate change treaty, which was ratified by 140 nations. Bush made a similar argument to the one outlined by Trump Thursday, saying it put the U.S. at a disadvantage compared with major polluters like China and India.

Still, Bush made the broad and public case for U.S. leadership in international cooperation, even as his policies in Iraq and Afghanistan frayed some American alliances.