Beyond Democrats, Sen. John McCain criticized Trump's desire to have Russia rejoin the group of economic powers. The Arizona Republican said Putin "chose to make Russia unworthy of membership in the G-8" and "nothing he has done since then has changed that most obvious fact."
"The President has inexplicably shown our adversaries the deference and esteem that should be reserved for our closest allies," McCain said in a statement. "Those nations that share our values and have sacrificed alongside us for decades are being treated with contempt. This is the antithesis of so-called 'principled realism' and a sure path to diminishing America's leadership in the world."
Sen. Jeff Flake, R-Ariz., flatly tweeted: "No, Russia should not be added to the G-7." Sen. Ben Sasse, R-Neb., also called Trump's posture "weak" and added that "Putin is not our friend and he is not the president's buddy," according to CNN.
Before Trump's statements Friday morning, G-7 allies even threatened to distance themselves from Washington. French President Emmanuel Macron said the group's six other members — France, Canada, Italy, Japan, Germany and the United Kingdom — could exclude Trump from a joint statement following the summit.
"The American President may not mind being isolated, but neither do we mind signing a 6 country agreement if need be. Because these 6 countries represent values, they represent an economic market which has the weight of history behind it and which is now a true international force," Macron tweeted.
Trump has lashed out at global trading partners ahead of the meetings in Canada. He contends barriers put up by allies have damaged American companies and workers.
"Looking forward to straightening out unfair Trade Deals with the G-7 countries. If it doesn't happen, we come out even better!" the president tweeted on Friday morning.
Trump and Macron were set for a bilateral meeting Friday morning amid the tensions, but Trump appeared to arrive in Canada too late to attend. The White House said it is working on rescheduling it.
On Thursday night, he called Canadian Prime Minister Justin Trudeau "indignant" for bringing up the strong relationship between the U.S. and Canada — despite trade practices that the president alleged hurt American farmers.
On Friday, Trump once again said he would scrap the North American Free Trade Agreement if the U.S., Canada and Mexico cannot strike a revised deal. His administration says failure to reach a new agreement contributed to its decision not to exempt Canada and Mexico from the tariffs on metals.