Roberto Azevedo said diplomats from the WTO’s 159 members tried hard but “cannot cross the finish line here in Geneva” ahead of a summit where ministers were to have signed the deal in Bali, Indonesia next week.

“The reality is that we have proved that we can’t cross the final yard here in Geneva. The process here is over,” Azevedo told reporters.

“This is not about shortness of time. If we had a few more weeks, we would still not make it,” he said.

“If we are to get this deal over the line, we will need political engagement and political will,” he added.

The diplomats became deadlocked over the details in the past few days and there remains so much disagreement that several more weeks of negotiations could close the gaps and it will not be possible to negotiate the final details in Bali, he said.

“Holding negotiations in the short time we’ll have in Bali would be simply impractical with over 100 ministers around the table,” he said.

In recent years, trade talks have progressed more speedily when they involved only two sides. The European Union, for example, has clinched free trade deals with South Korea and later Canada. It is in separate talks with the US and Japan as well.

But the failure to reach a global deal would “have grave consequences for the multilateral trade system” and hurt the WTO’s credibility, Azevedo said, because the organisation will only be viewed as a trade court and no longer as a forum for governments to negotiate trade agreements.

“We managed to make progress in a large number of very difficult areas,” Azevedo told a news conference. “Over the last few days, we stopped making the tough political calls. And this prevented us from getting to the finish line. We are indeed close, but not quite there.”

By some estimates, Azevedo noted, a final deal could provide a $1 trillion boost to global commerce.

But the talks have stalled as rich countries, emerging powers and the world’s poorest nations spar over the concessions needed.

Azevedo, however, cautioned that the splits were more complex.

“There is not a north-south divide,” he said.

One covers “trade facilitation”, which involves simplifying customs procedures in an effort to make commerce smoother, and where divisions centre on the time-lag developing countries would get to fall into line, plus the support they would get from donors to do so.

Another division is over “food security”, pushed by India, under which developing countries want to be allowed to subsidise grain stockpiling to help low-income farmers and consumers — stocks that critics warn could end up on the open market, skewing trade.