China accused the U.S. of abusing a national security exception at the World Trade Organization by cutting off Huawei Technologies Co. to American suppliers and warned the move could have grave consequences for the global trading system.

At a meeting of the WTO’s Committee on Market Access in Geneva on Tuesday, China said the U.S. had violated WTO rules and urged the Trump administration to “immediately lift all unilateral sanction measures against Chinese companies.”

Amid an escalating confrontation between the world’s two largest economies, President Donald Trump raised tariffs on $250 billion of Chinese exports this month and blacklisted Huawei as well as scores of its affiliates.

Talks on a trade deal have stalled and Trump warned Monday that tariffs on Chinese goods “could go up very, very substantially.” Trump said last week that Huawei could be part of the trade deal, though he called the company ”dangerous.”

Trump has also slapped tariffs on imported steel and aluminum and he’s considering imposing duties on foreign vehicles on the grounds of protecting national security.