GENEVA, July 3 (Reuters) – Major U.S. trading partners including the European Union, China and Japan voiced deep concern at the World Trade Organization (WTO) on Tuesday about possible U.S. measures imposing additional duties on imported autos and parts. Japan, which along with Russia had initiated the discussion at the WTO Council on Trade in Goods, warned that such measures could trigger a spiral of counter-measures and result in the collapse of the rules-based multilateral trading system, an official who attended the meeting said. Over 40 WTO members, including the 28 countries of the European Union – warned that the U.S. action could seriously disrupt the world market and threaten the WTO system, given the importance of cars to world trade. The United States has imposed tariffs on European steel and aluminium imports and is conducting another national security study that could lead to tariffs on imports of cars and car parts. Both sets of tariffs would be based on concerns about U.S. national security. U.S. President Donald Trump said on June 29 that the probe would be completed in 3-4 weeks. But the European Union has warned the United States that imposing import tariffs on cars and car parts would harm its own automotive industry and likely lead to counter-measures by its trading partners on $294 billion of U.S. exports. A Russian official told the WTO meeting that the issue of U.S. investigations had been raised over the past year in different WTO meetings, only to see things change for the worse. The United States was losing its reputation as a trusted trade partner, the Russian delegate told the meeting, adding that the United States could soon start an investigation into the case for import tariffs on uranium products. China, Canada, Switzerland, Norway, Turkey, Costa Rica, Hong Kong, Venezuela, Singapore, Brazil, South Korea, Mexico, Qatar, Thailand and India all echoed the same concerns and said they doubted the U.S. tariffs were in line with WTO rules. The U.S. diplomat at the meeting said the matter was already the subject of formal disputes at the WTO, so it should not be on the committee’s agenda, the official who attended the meeting said.