WASHINGTON - The United States has underestimated China's determination and capability to fight back in response to the US proposed steep tariffs on Chinese imports, a Chinese scholar said here on Monday.

"China was forced to take the action to fight back. There's no way for China to back off," said Ruan Zongze, executive vice president and senior research fellow of the China Institute of International Studies, a think tank affiliated with China's Ministry of Foreign Affairs.

"China has to defend its legitimate interests as well as the global multilateral trade regime," Ruan told reporters at the Chinese embassy in Washington.

Ruan, a former diplomat, said the United States "made a mistake twice" as President Donald Trump last week threatened tariffs on an additional $100 billion Chinese goods.

"I think Washington underestimates China's determination," he said.

"China has demonstrated its determination to strike back almost immediately" against US tariff proposals "with equal scale and equal strength," he said.

China last week unveiled a list of products worth $50 billion imported from the United States for a possible additional tariff of 25 percent, hours after the United States released a proposed list of $50 billion of Chinese products subject to an additional 25 percent tariff.

While the Trump administration attempted to calm the financial markets by talking of a possible deal with China, there are currently no formal trade talks between the two countries, said the scholar, adding that now "the ball is in America's court."

"China has said it will fight with comprehensive counter measures" if the United States continues its unilateral, protectionist practices, Ruan noted.

That means that "all options (are currently) on the table", including "trade in services, investment, finance, and many others," he said.

Ruan also pointed out that it's "unreasonable" for Trump to ask China to reduce its trade surplus with the United States by $100 billion.

China is only one link of the global supply chain and the US estimate of the trade surplus is exaggerated by about 20 percent, he added.

"We think that this kind of trade issue is largely decided by the market, not by the executive order," he said.