US President Donald Trump said on Wednesday that the ceasefire agreement reached this week with Iran was not final, and that he could resume a bombing campaign if he did ‌not like it.

"It's a memorandum of understanding. And if I don't like it, we'll go back to shooting at them, dropping bombs on their head," Trump said at a G7 summit in France.

"If I don't like it, if they don't behave, we'll go right back to dropping bombs right smack in the middle of their head, OK?"

Leaders of the G7 countries demanded a ceasefire in Lebanon on Wednesday and said they will diversify energy supply routes to reduce dependence on the Strait of Hormuz in response to the war in Iran, as they welcomed the interim deal to end it.

The leaders met for a summit in the French town of Evian-les-Bains, an hour's drive along the shore of Lake Geneva from where ⁠the memorandum is due to be signed at a ceremony across the Swiss border on Friday.

The US-Iran agreement is expected to launch negotiations towards a final settlement to end the war, which has killed more than 7,000 people, mostly in Iran and Lebanon.

"We underline the need for the negotiation ... to address the threats posed by Iran in the region and beyond and ensure that they never obtain a nuclear weapon," the leaders said in a statement.

The summit gave Trump a chance to present his deal with Iran to allies Britain, Canada, France, Germany, Italy and Japan.

-Reuters