FILE PHOTO: A U.S. flag is seen during a welcoming ceremony in Beijing, China, November 9, 2017. REUTERS/Thomas Peter/File Photo

BRUSSELS (Reuters) - The United States and the European Union must overcome their trade disputes and stand up to China’s “economic aggression” together, U.S. President Donald Trump’s new ambassador to the European Union said on Friday.

Gordon Sondland, a hotel magnate who was sworn in on June 30, said in an opinion piece for Politico Europe that Washington and Brussels needed to seize the new momentum created by a July agreement to avoid U.S. tariffs on European cars.

“I see real opportunities for the transatlantic relationship to be a force that curtails Chinese economic aggression and unfair trade practices,” Sondland said, citing concerns such as Chinese overproduction, state subsidies and rules requiring foreign companies to share their know-how with Chinese firms.

“We all share an interest in seeing China offer greater market access and eliminate unfair trade practices, and together we can insist China take the necessary steps to allow its economy to operate more fairly,” Sondland said, striking a constructive tone despite recent EU-U.S. tensions.

Trump’s decision to pull out of the Iran nuclear accord, his imposition of tariffs on EU metals exports and his insistence that European allies increase military spending and lower import tariffs have overturned long-standing, warm transatlantic ties.

Despite Trump’s tariffs on European exports, Brussels shares Washington’s concern about China’s closed markets and what Western governments say is Beijing’s domination of global trade through state intervention and subsidies.

However, the European Union and the United States differ on how to force Chinese reform, such as the removal of barriers to foreign investment.

Trump has hit China with billions of dollars of tariffs in July and is considering imposing tariffs on another $200 billion of Chinese imports. The European Union rejects that approach, instead relying on global forums such as the World Trade Organization to cut excess steel capacity and avoid market-distorting subsidies.