UN chief Ban Ki-moon made a last-ditch effort Thursday to break the deadlock over a landmark treaty to regulate the conventional arms trade, urging countries to “show flexibility.”

Ban issued a statement saying he was concerned at the “very limited progress” made during month-long negotiations in New York, where the world’s biggest arms producers have been haggling over the scope of the treaty.

Since the start, the United States has opposed the inclusion of ammunition, China does not want small arms and both Russia and China have sought restrictions on references to humanitarian law.

With talks due to end Friday on a first ever treaty to regulate the $70 billion a year industry, Ban urged the 193 UN member states to “show flexibility and work in good faith towards bridging their differences.”