What is the G7?It is an annual summit bringing together Canada, the US, the UK, France, Italy, Japan and Germany, which represent more than 60% of global net worth between them.
Economics tops the agenda, although the meetings now always branch off to cover major global issues.
Russia was suspended from the group in 2014 because of its annexation of Crimea from Ukraine. On Friday, Mr Trump made a surprise call for Moscow to be readmitted but German Chancellor Angela Merkel and other members were against the idea.
What are the tariffs?On 1 June, the US imposed a 25% tariff for steel and 10% for aluminium on imports from the EU, Canada, and Mexico. Mr Trump said the move would protect domestic producers that were vital to US security.
The EU then announced tariffs on US goods ranging from Harley-Davidson motorcycles to bourbon. Canada and Mexico are also taking action in retaliation.
US President Donald Trump has retracted his endorsement of the joint communique issued at the end of the G7 summit, accusing Canada of "dishonesty".He said that other countries were imposing "massive tariffs" on the US.
The joint communique, advocating a "rules-based trading system", was reached despite tension over US tariffs on steel and aluminium imports.
Canadian Prime Minister Justin Trudeau vowed afterwards to press ahead with retaliatory tariffs on 1 July.
Speaking at a news conference, he described as "insulting" Mr Trump's decision to invoke national security concerns to justify steel and aluminium tariffs.
"It would be with regret but it would be with absolute clarity and firmness that we move forward with retaliatory measures on 1 July," Mr Trudeau said. "Canadians are polite and reasonable but we will also not be pushed around."
His speech contained nothing he had not said before, both in public and in private conversations with Mr Trump, his office said later.
The EU said it would stick to the joint communique despite Mr Trump's decision.
"We stand by the commitments made in the G7 communique," a senior UK government source said.
Tweeting en route to his next summit in Singapore, Mr Trump said he had instructed US officials "not to endorse the communique as we look at tariffs on automobiles".
He said the move was based on Mr Trudeau's "false statements at his news conference, and the fact that Canada is charging massive tariffs to our US farmers, workers and companies".
He suggested Mr Trudeau was "very dishonest and weak".
PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, “US Tariffs were kind of insulting” and he “will not be pushed around.” Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!
Canada talks tough
Until just a few weeks ago, the relationship between Mr Trump and Mr Trudeau could have been called cordial. Despite differences between the two countries over trade - from tiffs over everything from softwood lumber and newsprint to the major renegotiation of the trilateral North American Free Trade Agreement - the two men tended to speak positively about each other.In the communique, the group of major industrial nations - Canada, the US, the UK, France, Italy, Japan and Germany - agreed on the need for "free, fair, and mutually beneficial trade" and the importance of fighting protectionism.
"We strive to reduce tariff barriers, non-tariff barriers and subsidies," they said.
Other agreements reached include:
- Russia: A joint demand that Moscow "cease with its destabilising behaviour". The leaders called on the Kremlin to stop with its attempts to "undermine democracy" and to withdraw its support for Syrian President Bashar al-Assad
- Iran: A pledge to "permanently" ensure Tehran's nuclear programme remains peaceful. The group said they were committed to ensuring Iran would "never seek, develop or acquire a nuclear weapon"
- Climate: An agreement to disagree. The US refused to sign a pledge to implement the Paris climate change accord after Mr Trump announced he was pulling out of the agreement last June in the hope of a new "fair" deal
What else did Trump have to say?President Trump earlier told reporters he had proposed the idea of a tariff-free G7 to other leaders and described his talks with them as "extremely productive".
"The United States has been taken advantage of for decades and decades," he continued, describing America as a "piggy bank that everyone keeps robbing".
President Trump said retaliation tariffs from his allies were a "mistake" and warned that if it got as far as a trade war, then the US would "win that war a thousand times out of a thousand".