McCain took to Twitter to express his displeasure.
Trump withdrew his support for the G7 joint communiqué in a series of messages sent Saturday that blasted Canadian Prime Minister Justin Trudeau after Trudeau said Canada would "with absolute certainty" impose retaliatory measures on the us over tariffs, CNN reported.
In his final news conference before leaving, Mr Trump said trade was at the top of the agenda and the USA has been taken advantage of for decades and it cannot go on.
French President Emmanuel Macron, for example, noted that under European Union rules France now has open borders with Britain and Germany and runs trade deficits with both - far from Trump's vision of "reciprocal" balanced trade.
Trump had told Trudeau any retaliation would be a mistake and the prime minister agreed that it was "not something we want to do".
Tensions between the U.S. and its G7 partners over trade and the United States withdrawal from the Iran nuclear deal were rife in the face of the summit which had been dubbed by some as "G6 plus one", referring to an isolated US.
Because of the disputes, many observers were not certain a statement would be issued under all seven countries' names.More news: Trump wants Russian Federation to rejoin G-7
According to multiple reports, Trump brought up the idea of totally free trade during a meeting with the other G7 leaders which include the heads of Canada, France, Germany, Italy, Japan, the United Kingdom, and representative for the EU.
Before leaving the White House Friday to travel to the summit, Trump called for Russian Federation to be readmitted to the group. I think it would be good for the United States.
Merkel's proposal was strongly supported by other leaders at the meeting, the official said, adding that European Commission President Juncker said he was ready to invest personally in it.
"The president will continue to say what he says at various occasions". Crimea was let go during the Obama administration.
By ordering his representatives to back out of the communique, Trump appeared to be asserting his oft-stated aim of upsetting the status quo whether by pulling out of the global climate accord or the worldwide nuclear deal with Iran or threats to scrap the North American Free Trade Agreement.
Trump said he doesn't blame the current leaders, but he had a sharp warning for them if they don't work with him to correct what he sees as an unfair situation. "I would say that the G-8 is a more meaningful group than the G-7, absolutely", he told reporters as he left the summit in Canada.
Trump warned countries against levying retaliatory tariffs on the USA after his administration imposed punitive tariffs on aluminum and steel imports from Canada, Mexico, and the European Union on national security grounds.
These moves are the clearest sign yet that Trump intends to shake up an global trade and security order built by the USA after World War II and carefully cultivated since then by successive administrations, Republican and Democrat. In fact, when the two met in France past year, Trump and Macron could be seen clenching fists in an awkward handshake until both of their knuckles turned white.