The White House announced his travel plans after French President Emmanuel Macron and Canadian Prime Minister Justin Trudeau signaled they will use the event to take a stance against new US tariffs on steel and aluminum imports.
Just days before Trudeau is set to host a G7 Summit in Quebec, Canadian officials tell CNN they are just trying to "keep Trump happy".
Trump's tweet comes ahead of his arrival at the G7 Summit in Quebec on Friday, where both Trudeau and Macron are expected to push him to reconsider his imposition of steel and aluminum tariffs on his G7 partners. But "neither do we mind signing a 6 country agreement if need be".
"These six represent values, represent an economic market, and more than anything, represent a real force at the global level today", Macron said.
Japanese Prime Minister Shinzo Abe met with Trump at the White House on Thursday where the focus was Trump's unprecedented meeting with the North Korean leader scheduled for Singapore next week. Signaling that his allies would not be intimated, Macron made it clear that the other six countries at G7 meeting would gladly sign deal without Trump.
But they expressed support for the US president's historic meeting in Singapore with North Korean leader Kim Jong Un, scheduled to take place early next week.
Trump threatened to impose even more tariffs against those countries if they did not take down their barriers to United States trade.
It's safe to say this is going to be one interesting trip.
"Please tell Prime Minister Trudeau and President Macron that they are charging the USA massive tariffs and create non-monetary barriers", he tweeted.
Macron, who appeared to have built a warm relationship, said the "G6" leaders would not spark a fight at the summit.
Canada's Trade Minister Francois Philippe Champagne was even more blunt, declaring: "What we are seeing is that the world economic order is under pressure, under attack".
Trump will likely have to meet all of them again, with the exception of Paolo Gentiloni, who is no longer Italian Prime Minister.
Despite his "bromance" with Trump, he too let the USA leader know he's not pleased with the new tariffs on steel and aluminum.
The summit threatens to mark the outer limit of worldwide patience for the avowed nationalistic Trump, as leaders who had sought to cajole and "bromance" the president are embracing more hard-nosed tactics. POTUS reportedly then said to the PM, "Didn't you guys burn down the White House?" The nuclear agreement included Germany and the five permanent members of the United Nations Security Council, which includes France and Britain - all G7 members. "So I don't think there's any issue there at all". The United States trade representative office told the Washington Post that the US actually has a trade surplus with Canada. The European Union also attends.
Two sources in Ottawa said divisions between the United States and other G7 members were so great that senior officials in charge of each nation's preparations planned to hold an unusual additional meeting the night before the summit in a bid to find consensus.
Trump is set to visit the United Kingdom in a July visit where he will meet the Queen, enjoy a jaunt around his Scottish golf course, and presumably face off with protesters already vying to speak out against the president during his United Kingdom stay.