BUENOS AIRES—The finance ministers and central bankers of the G-20 group of countries ended their meeting here with little progress on resolving global trade tensions sparked by President Donald Trump’s tariffs, with the U.S. and EU both insisting their conditions for trade talks must be met.

U.S. Treasury Secretary Steven Mnuchin got the ball rolling Saturday morning when he told reporters that the U.S. is ready to start talks on trade agreements with China, the EU and the Japanese, but that those trading partners must first...