(Bloomberg) -- China made a mistake in putting tariffs on soybeans right at the start of the dispute with the U.S., and it needs to focus on the current problems, not try and get involved in politics, according to Long Yongtu, a former official who negotiated the nation’s entry into the World Trade Organisation.

When the U.S. imposed tariffs earlier this year, "I said that China should only retaliate against U.S. agricultural exports as a last resort," Long said on Sunday at a Caixin forum in Beijing. "Based on my experience of Sino-U.S trade, I said at the time that agricultural products are very sensitive, and soybeans are very sensitive too. We should have avoided targeting soybeans in our original response."

The Chinese tariffs on the beans have left U.S. farmers struggling to sell their crop, and was widely seen in the U.S. as an attempt to sway support for President Donald Trump in Iowa and other farm states which he won in the 2016 election. Chinese state media placed a supplement in Iowa’s largest newspaper blaming Trump for the trade dispute, and he responded by accusing the nation of trying to interfere in the U.S. mid-term elections.

The Chinese decision to target a product that it needs makes people think there is an ulterior motive, Long, who was the vice minister for trade during China’s accession to the WTO and is now co-chair at the Center for China and Globalization, said. "I don’t like complex motives. Let’s take the matter on its merits."

"When discussing tariffs, let’s just focus on the tariff. When negotiating about the car industry, let’s just focus on the car industry," he said. "Nothing will come of the discussions if the negotiators are thinking about politics."

--With assistance from Zoe Ma and Miao Han.

To contact Bloomberg News staff for this story: Lucille Liu in Beijing at xliu621@bloomberg.net

To contact the editors responsible for this story: Jeffrey Black at jblack25@bloomberg.net, James Mayger

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