EVIAN : Canada's Prime Minister Mark Carney on Wednesday said a US-Iran deal to end the Middle East war could be a "game changer" in the region and beyond.

There is "a likelihood that this memorandum of understanding agreement could be a game changer", Carney told reporters on the third day of a G7 leaders' meeting in the French town of Evian.

He pointed to encouraging discussions, which included US President Donald Trump, on Ukraine and Lebanon at the summit.

The Canadian premier said he noted a US "change in tone with respect to Ukraine" as Kyiv seeks to end more than four years of conflict following Russia's invasion.

This included "a more realistic -- in our view -- expectation of where this war was going to go, and the position against Russia, the tightening of sanctions against Russia, the ability to provide additional defensive support for Ukraine".

The leaders of Canada, France, Germany, Italy, Japan, Britain and the United States also held a "very detailed discussion about Lebanon", he added.

The talks on a final US-Iran settlement to end the conflict, triggered by the February 28 US-Israeli strikes on Tehran, are set to begin Friday immediately after the signing of the accord in Switzerland and continue over a 60-day window to flesh out its details.

But fresh Israeli strikes on alleged Iran-backed Hezbollah sites in south Lebanon have dented the optimism surrounding the deal.

"Yes, there are risks. Yes, the accord has to be put into place," said Carney.

"But the very fact of it -- and the fact that so many countries were involved in its development and are vested in its development -- does create knock-on effects, positive knock-on effects," he said.

In a joint statement late on Tuesday, the G7 hailed "the breakthrough and the opportunity that currently exist in the Middle East".

They said the memorandum of understanding "provides an historic opportunity to prevent Iran from acquiring any nuclear weapon and tackling the threats related to its regional and ballistic activities".