The United States is taking aim at “excessive” business class air travel by UN staff as it presses a campaign to restrain the global body’s multi-billion dollar budget.

Complaints by the United States and other cash-strapped western nations have been bolstered by revelations that nearly three quarters of the money spent on air fares at UN headquarters goes on business class.

That is “clearly unjustifiable,” said Joseph Torsella, the US envoy who since 2011 has been leading a US war on “waste” at the UN.