Global trade is not the main cause for the loss of manufacturing jobs in places like the United States and needs to be defended from its critics, the chief of the World Trade Organization said Wednesday.

Director-General Roberto Azevedo rebuffed arguments made by some politicians around the world, such as U.S. presidential candidate Donald Trump, that global trade deals are destroying jobs or causing them to move to lower-cost countries.

He pointed to recent studies showing that as much as 90 percent of the U.S. manufacturing jobs recently lost were due to new technologies, innovation or improvements in efficiency.

"It had nothing to do with imports, it had nothing to do with trade competition," he told reporters after a WTO general council meeting. "I don't think we do enough in making the case for trade because we think trade is so obviously positive for any economy. It's like trying to argue with a friend that he needs to breathe."

He declined to comment on weekend remarks by Trump to NBC TV suggesting Trump might pull the U.S. out of the WTO if its rules prevent his hopes to set fees on U.S. companies that ship jobs abroad.

"I don't intend to get into a debate," Azevedo said. "I'm not a candidate."

The Brazilian instead announced plans to seek a second four-term at the organization's helm and lamented troubles in world trade.

"We are in a particularly sensitive moment in the global economy with economic volatility, low growth and weak trade expansion," he said. "We are seeing the weakest five-year period of trade growth since the 1980s."

Azevedo defended the WTO's role in helping to resolve disputes like a recent U.S. complaint alleging China unfairly limits raw materials exports, hurting U.S. manufacturers.

Asked about the impact of Britain's vote to quit the European Union on international trade, Azevedo said WTO officials were "still exploring" the consequences.

"We have no precedent for this. This is the first time that ... if it actually happens, and when it does happen, we would have a WTO member without a schedule of commitments," he said.

Alluding to Britain, Azevedo said: "You don't unilaterally decide what your commitments are with the other members. We'll have to negotiate those commitments ... How do you get there? It could be very simple, or it could be very convoluted and complicated."