Trump had originally planned to depart Canada for Washington on Tuesday (Wednesday AEST).
"I have to be back as soon as I can," the president told reporters at the summit in Kananaskis in the Canadian Rockies.
The G7 has struggled to find unity over conflicts in Ukraine and between Israel and Iran as Trump overtly expressed support for Russian President Vladimir Putin and has imposed tariffs on many of the allies present.
Trump had earlier urged everyone to immediately evacuate Tehran, and reiterated that Iran should have signed a nuclear deal with the United States.
The US president will leave Canada after having dinner with the other heads of state, Press Secretary Karoline Leavitt confirmed.
"Much was accomplished, but because of what's going on in the Middle East, President Trump will be leaving tonight after dinner with Heads of State," Leavitt wrote on X.
French President Emmanuel Macron said Trump's departure was positive, given the objective to get a ceasefire in the Middle East.
G7 leaders from Britain, Canada, France, Germany, Italy, Japan, and the US, along with the European Union, had convened in the resort area of Kananaskis in the Canadian Rockies until Tuesday.
Speaking alongside Canadian Prime Minister Mark Carney earlier, Trump said the former Group of Eight had been wrong to kick out Russia in 2014 after it annexed Crimea.
"This was a big mistake," Trump said, adding he believed Russia would not have invaded Ukraine in 2022 had Putin not been ejected.
"Putin speaks to me. He doesn't speak to anybody else ... he's not a happy person about it. I can tell you that he basically doesn't even speak to the people that threw him out, and I agree with him," Trump said.
Though Trump stopped short of saying Russia should be reinstated in the group, his comments had raised doubts about how much Ukrainian President Volodymyr Zelenskiy can achieve when he is schedule to meet the leaders on Tuesday.
European nations had wanted to persuade Trump to back tougher sanctions on Moscow.
Zelenskiy said he had planned to discuss new weapons purchases for Ukraine with Trump.
European officials said they hoped to use Tuesday's meeting with Zelenskiy and NATO Secretary General Mark Rutte and next week's NATO summit to convince Trump to toughen his stance.
In another early sign the group of democracies lacked unity, a US official said Trump would not sign a draft statement calling for de-escalation of the Israel-Iran conflict.
Canada has abandoned any effort to adopt a comprehensive communique to avert a repeat of the 2018 summit in Quebec, when Trump instructed the US delegation to withdraw its approval of the final communique after leaving.
Leaders have prepared several draft documents seen by Reuters, including on migration, artificial intelligence, and critical minerals. None of them have been approved by the United States, however, according to sources briefed on the documents.
Without Trump, it is unclear if there will be any declarations, a European diplomat said.
Carney invited non-G7 members Mexico, India, Australia, South Africa, South Korea and Brazil, as well as Ukraine.
Carney said in a statement he had agreed with Trump that their two nations should try to wrap up a new economic and security deal within 30 days.
Trump said a new economic deal with host Canada was possible but stressed tariffs had to play a role, a position the Canadian government strongly opposes.
with Reuters and DPA
8°C