With a trade war's dark clouds hanging over the China-US relationship, some down-to-earth wisdom and far-reaching optimism from both sides could help energize communication channels.

There should be a consensus that China and the US, the two largest economies in the world, have far more common interests than differences.

Fortunately, goodwill and faith have been expressed in California, which hopefully can reach policymakers.

At an event on Sept 21 to celebrate the 69th anniversary of the founding of the People's Republic of China, Betty Yee, California's state controller since 2015, delivered an inspirational message.

Speaking to the 800 attendees at the reception, Yee discussed how stable, consistent collaboration between the Golden State and China has benefited both.

Noting that China sent a 100-member strong delegation to the Global Climate Action Summit in San Francisco from Sept 12-15, Yee said that "as we tackle some of the global challenges, we need China. We need exchange of ideas and knowledge with China."

May the model of cooperation between California and China "begin to show the way for our government in Washington DC – it's here in California that trade matters," said Yee, adding that "every economic sector, from agriculture to the mining industry to technology, it's affected by the (current) trade relationship (backlash)."

In 2017, bilateral trade between China and the US was $583.7 billion, 233 times that of 1979, the year the two nations formalized a bilateral relationship, said Wang Donghua, consul general at the Chinese Consulate General in San Francisco, who added that two-way investment has reached $200 billion over the years.

For example, Apple's sales volume to China in 2017 was $44.76 billion, and the company sold 50.26 million cellphone units there, 19.6 percent of its global total. Also last year, Boeing delivered 202 aircraft, 26 percent of its global total, to China, its largest foreign market.

The two sides need mutually beneficial cooperation in promoting their respective development and for coping with common challenges far more than at any time in the past, said the diplomat who reported to his post on Aug 8. "It can be said that cooperation has brought more opportunities to both sides and achieved mutual benefits. China and the US are important partners rather than strategic rivals."

It is also normal that competition exists in China-US cooperation, said Wang, adding that the purpose of competition is to promote mutual development rather than suppress or curb the development of the other.

China-US relations are now facing difficulties, and the trade war is constantly escalating, Wang warned.

"This unilateralism and protectionist approach will result in no winners and will heavily hit the global industrial chain as well as seriously hurt the interests of enterprises and the general public in many countries, including the US," he said.

Frank Wu, president of the Committee of 100, who teaches at the University of California's Hastings College of the Law, said trade wars have almost always been bad, regardless of which side you are on.

"In American history, the Smoot-Hawley Act in 1930 accelerated the Great Depression. From today's vantage point, just about everyone agrees those tariffs made matters worse," he said.

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