Trump cited unfair trade and tariffs from Canada, a longtime USA ally, as one of the reasons he refused to back the joint statement.
Nearly 18 months into Trump's presidency, Merkel's comments offered renewed evidence of Germany's struggle to adapt to an upended relationship with the US.
Captured and circulated by Mr Trump's team, another photo doesn't even show Mrs Merkel as the Republican firebrand takes centre stage in the middle of a crowd of world leaders who look to get his attention. The official said disagreements remain, particularly with the US on a number of issues, but the goal remains to reach agreement on all the big issues. National Security Adviser John Bolton and other aides also look on what appears to be a tense moment. She also said the U.S. president wasn't entirely wrong in pressing Germany to increase defence spending. He said he was unhappy at an end-of-summit press conference by Trudeau after he left the summit, in which Trudeau said Canada would retaliate against US trade tariffs. Larry Kudlow, Trump's chief economic adviser, accused Trudeau of undermining USA interests at the summit, calling Trudeau's actions "a betrayal".
Elisabeth Wehling, a US-based political linguistics researcher, tweeted that the body language clearly pointed to Trump dominating the scene. We have a very big trade deficit with Canada.
Trump had delivered a stark warning to America's trading partners not to counter his decision to impose tariffs on steel and aluminum imports.
The 28-member bloc - soon to lose the United Kingdom after the 2016 referendum to exit the European Union - managed to grapple with a financial meltdown and the biggest influx of refugees since World War II only with "great effort", Merkel said.