WASHINGTON — President Donald Trump declared Thursday he was pulling the U.S. from the landmark Paris climate agreement, striking a major blow to worldwide efforts to combat global warming and distancing the country from its closest allies abroad. Framing his decision as "a reassertion of America's sovereignty," Trump said he was "elected to represent the citizens of Pittsburgh, not Paris."He said the U.S. could try to re-enter the deal under more favorable terms or work to establish "an entirely new transaction." But he indicated that was hardly a priority.