The fate of the World Trade Organization's (WTO) top court was effectively sealed on Monday after the United States said it would not back a proposal to allow it to continue, trade officials said, although the WTO chief vowed to find a solution.

The WTO appeals panel, sometimes dubbed the supreme court of world trade, will no longer have the needed quorum of three judges as of midnight on Tuesday, due to mandatory retirements.

The Trump administration has been blocking appointments to the WTO's seven-member Appellate Body that rules on trade disputes for more than two years.

WTO director-general Roberto Azevedo said that a "well-functioning, impartial and binding dispute settlement system is a core pillar of the WTO system," adding. "We cannot abandon what must be our priority, namely finding a permanent solution for the Appellate Body."

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Azevedo said that he would "launch more intensive, high-level consultations on how to resolve the longstanding impasse."

Zhang Xiangchen, China's trade ambassador, said, "This is no doubt the most severe blow to the multilateral trading system since its establishment."

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João Aguiar Machado, the European Union's ambassador, put the blame squarely on Washington.

"In two days from now, we will have an unprecedented situation in the World Trade Organization, which will no longer be able to deliver binding resolution of trade disputes and will no longer guarantee the right to appeal review," Machado said.

"The actions of one member will deprive other members of their right to a binding and two-step dispute settlement system, even though this right is specifically envisaged in the WTO contract," he said.

Ten pending appeals would be left in limbo, along with a 100 or so more further back in the system.

(With input from Reuters, AFP)