By Emma Farge and Philip Blenkinsop

World Trade Organization head Roberto Azevedo will step down a year earlier than planned in August, he said on Thursday, in a surprise move as the trade body struggles to rein in global tensions and coordinate responses to the COVID-19 pandemic.

The 62-year-old Brazilian has been director-general since 2013 and is serving a second term that was due to conclude at the end of August 2021.

Azevedo said he had taken a "personal decision" after talking with his family and that his move was not due to health reasons or specific political ambitions.

In a text of remarks to the WTO's members, Azevedo said he thought it was also in the best interests of the organisation.

"As members start to shape the WTO's agenda for the new post-COVID realities, they should do so with a new director-general," he told a virtual WTO meeting on Thursday afternoon.

His departure comes as the 25-year-old body's role in settling disputes has been undermined after its Appellate Body was paralysed in December by Washington's decision to block the appointment of judges.

Asked about Azevedo's departure, U.S. President Donald Trump said he was "OK with it," telling reporters the WTO was "horrible."

"We've been treated very badly," he said. "They treat China as a developing nation. Therefore China gets a lot of the benefits that the U.S. doesn't get."

Senator Josh Hawley, a fellow Republican, this week introduced a resolution to withdraw from the WTO, blaming it for favoring China and "hollowing out American industry."

"NEW NORMAL" AFTER COVID-19

Since the COVID-19 crisis hit, Azevedo has called for governments to refrain from imposing export restrictions on food and medical supplies.

The WTO club of 164 members, which is designed to set global trading rules, has not produced any major international accord since abandoning its "Doha Round" of negotiations in 2015.

Its members are negotiating an agreement to cut fishing subsidies to allow a revival of depleted fish stocks, while a smaller group is working on a possible e-commerce deal. However, key differences remain.

Some members, notably the United States, Japan and the European Union, are pushing for more fundamental reforms. They say global trading rules need to reflect a far stronger China and tackle state-led subsidies and forced technology transfers.

Such issues might have been addressed at the WTO's biennial meeting due to have taken place in Kazakhstan in June. That has now been pushed back to mid- or late-2021. Azevedo said his departure would allow a successor to be in place before then.

Azevedo said the WTO could not stand still while the world around it changed, nor ignore the "new normal" that emerged from the COVID-19 pandemic.

U.S. Trade Representative Robert Lighthizer said Azevedo would be difficult to replace and that Washington looked forward to participating in the process of selecting a successor.

Rufus Yerxa, president of the 100-member U.S. National Foreign Trade Council, called for a successor who would continue reforms and fight "the inevitable wave of protectionism that will emerge in a post-pandemic world."

"The biggest danger now is that critics will use a leadership vacuum as an excuse to undermine the entire system," he said in a statement.

EU Trade Commissioner Phil Hogan said a new chief should be found this year as the WTO was encountering major challenges and louder voices demanding reform.

Simon Evenett, professor of international trade at Switzerland's University of St. Gallen, said the next director-general would need to put the WTO back together again.

"The next leader of the WTO must command respect in the corridors of power of the major players. This is not the time to promote another ambassador. Someone with very senior government experience or global status is needed," Evenett said.

Azevedo was a career diplomat, while his predecessors have mostly had political backgrounds.

(Reporting by Emma Farge and Philip Blenkinsop; additional reporting by Jeff Mason in Washington; Editing by Peter Graff, Hugh Lawson, Lisa Shumaker and Richard Chang)