The tensions between the U.S. and China erupted at the World Trade Organization on Tuesday, with Washington’s envoy deriding China’s posture as “the self-proclaimed defender of free trade.”

At a meeting in Geneva of the WTO’s General Council, China’s ambassador took the floor to accuse the U.S. of taking the organization “hostage” by blocking judicial appointments that are necessary to resolve trade disputes between countries.

“The U.S. is abusing the decision-making mechanism of consensus,” said Zhang Xiangchen, who called Washington’s actions “dangerous and devastating.”

He also criticized President Trump’s proposed tariffs on $150 billion of Chinese goods.

But U.S. Ambassador Dennis Shea, in his first address to the council, urged the WTO to “confront the havoc created by China’s state capitalism” and defended U.S. actions as a justified response to Chinese trade policy.

“We have now entered the realm of Alice in Wonderland,” he told the council. “White is black. Up is down.”

“It is amazing to watch a country that is the world’s most protectionist, mercantilist economy position itself as the self-proclaimed defender of free trade and the global trading system,” Shea added. “The WTO must avoid falling down this rabbit hole into a fantasy world, lest it lose all credibility.”

China had put the issue of WTO’s trade dispute adjudication system on the agenda. “The United States has vetoed new appointments to the Appellate Body, causing a crisis at what is effectively the supreme court of world trade,” Reuters said.

Shea blamed the Appellate Body’s judges for a “steadily worsening rupture of trust.”

“Something has gone terribly wrong in this system when those charged with adjudicating the rules are so consistently disregarding those very rules,” he complained.

WTO spokesman Keith Rockwell described the meeting as “extraordinary in its intensity.”

“We had the two most powerful members of the WTO weighing in on their views of each others’ policy in a way I have not seen in my many years here,” he said.