US President Donald Trump has expressed confidence in reaching an agreement on the Iranian nuclear program.

"As I've been saying, I think a deal will be signed, or something will happen, but a deal will be signed, and I think Iran is foolish not to sign," Trump told reporters on the sidelines of the G7 summit.

Trump noted that diplomatic progress between the US and Iran can be expected in the coming days.

"I think Iran basically is at the negotiating table where they want to make a deal," the US president added.