European Union lawmakers and officials have condemned the United States for threatening the existence of the World Trade Organization's dispute settlement mechanism and vowed to do all they can to preserve a rules-based global trading system.

Cecilia Malmstrom, the outgoing European trade commissioner, said the EU and countries elsewhere have led efforts in the past two years to resolve the impasse related to the Appellate Body, where WTO members appeal for dispute resolution.

"This is not the dispute between the EU and the US. This is the dispute between the 163 members of the WTO and the US," she told members of European Parliament meeting in Strasbourg on Tuesday night for their plenary session.

The US has blocked the appointments of new judges to the body. And if no new appointments were made by Dec 10, the Appellate Body will cease to function due to a lack of the minimum number of judges required.

"Despite all these efforts, the Appellate Body very likely will come to a halt on the 11th of December. That's why we need to send this very clear message of determination," she said.

"We will do what it takes to preserve a binding, independent, twostep system of dispute resolution in the WTO."

Malmstrom said the EU will continue to support efforts that lead to a resolution over the appointments standoff, but it must prepare contingency measures if they remain blocked.

The EU reached agreements with Norway in October and with Canada in July for an interim appeal system in case the Appellate Body ceases to function.

Malmstrom stressed that it is not an alternative system that creates a "new normal" without the US. "It's an ad hoc solution with certain partners, hopefully leading to a plurilateral system that can work and to create some clarity and predictability for our companies," she said.

"We hope this can only be temporary. We owe that to our companies and to our citizens, because they are the ones benefiting from the system."

Christophe Hansen, a Luxembourg MEP from the European People's Party, said the EPP and other groups want to sound the alarm for the future of the international rules-based trading order.

"When the US last Friday blocked the appointment of two new judges to the Appellate Body for the 29th consecutive time in two years, they brought us one step closer to the brink," he said.

Hansen said all WTO members carry the responsibility to support the system that has allowed global rivals to compete with a single rule book to the benefit of all.

Marie-Pierre Vedrenne, a French MEP from the Renew Europe group, accused the administration of US President Donald Trump of showing a desire to "bury the multilateral system".

Swedish MEP Karin Karlsbro, also from the Renew Europe group, said the WTO was supposed to be a guarantor for international trade. "But right now the whole system is at risk from the ground up in line with President Trump's America First policy,... she said. "We need to stand by our principles."

Ellie Chowns, a UK MEP from the Greens group, said the Greens want fair rules for the trading system and the rule of law - not the law of the jungle. "But the way forward to achieve the reform requires countries to work together - dialogue not confrontation," she said.

Chowns described the US action as "not the action of a country engaging constructively to solve multilateral problems". "Frankly, it is the action of a country throwing its weight around," she said.

"We cannot allow 11th of December to be the day that the US unilaterally tears up the rule book. That's in nobody's interest."