Boris Johnson has visited Iraq to meet British troops helping to train local fighters involved in the war against Islamic State (IS).
The London mayor met soldiers training the Kurdish Peshmerga forces.
Mr Johnson was pictured posing with an AK-47 during his visit.
But, the London Assembly's Labour Party said people could be "forgiven" for thinking it was a "photo opportunity... to boost Boris' leadership".
It said Mr Johnson's trip to meet soldiers on the frontline was more about the mayor's "leadership ambitions than it is about delivering for London".
But the mayor contested its stance.
He said: "We have a mutual interest in not only Kurdistan region's security and prosperity, but that of Iraq as a whole," the London mayor said.
"Over the last decade, Kurdistan region has seen considerable economic growth and social development, and I'm here to mark London's role as an active ally in this.
"The links between Britain and the Kurdistan region are developing at an incredible pace, there is a dynamic and forward-looking leadership here, and I am looking forward to rolling up our sleeves and discussing greater co-operation on a range of issues."
The Kurdish Peshmerga forces have been involved in some of the heaviest fighting against IS.
The mayor was accompanied on the visit by the British consul general to Kurdistan Angus McKee and Tory MP Nadhim Zahawi, who was born to Kurdish parents in Iraq and retains close links with the region.
Mr Johnson visited the airport in the region's capital Irbil to see the work of the British companies involved in building and running it.
He was briefed on the airport management's desire to secure the first direct flights to London from the city, which it is hoped would boost to trade between the UK and Kurdistan.