Warmer temperatures are melting Arctic ice and raising tensions as the U.S. looks to expand its presence in newly open waters. The problem: Russia and China also have growing trade, energy and military ambitions there. Photo composite: Ksenia Shaikhutdinova WASHINGTON—Senior U.S. and Chinese officials said they were committed to carrying out the phase-one trade accord between the two nations, the two governments said, after the two sides discussed the pact Monday evening U.S. time. The videoconference brought together U.S. Trade Representative Robert Lighthizer, Treasury Secretary Steven Mnuchin and Chinese Vice Premier Liu He for a formal review of the trade deal signed in January. The trade representative’s office released a one-paragraph summary of the talks, which it said…