In the four months since the leaders last met, Xi Jinping has overseen a surge in China's trade with the world while Trump has struggled with falling approval ratings.

He said the arch would double as a "military complex" housing drones and snipers, as well as storing ammunition.

Researchers said the total sea-level rise from ice losses may not sound like a huge number, but it puts 6 to 9 million people at risk of flooding and erosion.