France told its G7 partners of the Iranian foreign minister's surprise visit for side talks at a summit as soon as it was possible, a French official said on Sunday, after the White House said the move had surprised President Donald Trump.

"It was all organised at very short notice," an Elysee official told Reuters. "It all happened within a small window. Other countries were informed as soon as possible. It all happened in a matter of hours."

Asked why other countries weren't told earlier of the surprise visit, the Elysee official said: "They were informed early enough," adding that the diplomatic situation was too sensitive.

Iran's foreign minister flew in for side talks at the G7 summit on Sunday as host France ramped up efforts to ease tensions between Tehran and Washington.