Brazil's WTO ambassador Roberto Azevedo and his rival Herminio Blanco, Mexico's former trade minister, are expected to learn as early as Tuesday whether they have won a contest that is seen as too close to call.
All concerned are keenly aware that the successor to two-term director general Pascal Lamy from France must act fast to revive the WTO's moribund global trade talks.
Both men have pitched a similar vision for a negotiating process which they say needs overhauling.
Blanco, meanwhile, said it was time to reboot the 159-nation WTO.
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"The main challenge is the 'W' in 'WTO'," he told AFP, underlining that the logjam had pushed members into negotiating bilateral and regional deals.
"You have to transfer this energy back to Geneva," where the WTO is based, to prove the point and reach of the organisation, he said.
Supporters of a WTO-wide deal warn that other accords can create a "spaghetti bowl" of conflicting rules, thereby failing to serve global commerce.
The stated goal of its "Doha Round", launched at a summit in Qatar in 2001, is to deploy trade to develop poorer economies.
But members repeatedly have clashed over the give and take needed to reach a deal, with deep splits notably between China, the European Union, India and the United States.
Some have blamed Lamy, a former EU trade chief, who raised hackles with an alleged name-and-shame drive to break the deadlock after he won a second term in 2009.
"The new DG obviously will come in at a rather precarious time for the WTO," said Sergio Marchi, Canada's former trade minister and ex-WTO ambassador.
Besides working the diplomatic circuit, Marchi told AFP, the new leader must repair ties with the business community -- the hub of global commerce.