(Bloomberg) -- The worsening trade war is driving the steepest selloff in Chinese shares traded in the U.S since the global financial crisis.

The S&P/BNY Mellon China ADR Index has plunged 15% this month, putting it on track for its worst monthly performance since October 2008. Social media firm Weibo Corp., online media company Sina Corp. and Internet search firm Baidu Inc. have all declined more than 30%. Losses aren’t confined to the U.S. -- in Hong Kong, the Hang Seng China Enterprises Index of mainland companies is down about 10%, the worst performance among major global benchmarks.

The scale of the rout shows how tainted Chinese assets have become since the Trump administration stepped up pressure against Beijing this month by imposing tariffs and taking steps to limit the country’s access to key technologies. Just three weeks ago the S&P/BNY Mellon’s ADR index was nearing a nine-month high, while Shanghai’s equity benchmark first quarter performance was its best three-month gain in more than four years.

The timing of the slump is bad news for investors who track MSCI Inc.’s global benchmarks. The index compiler is increasing weightings of Chinese mainland-listed companies in its gauges, which are already heavily dominated by overseas-traded Chinese firms. Chinese companies have contributed to more than a quarter of this month’s declines on the MSCI Emerging Markets Index, led by Tencent Holdings Ltd.

A slumping yuan is adding to investor pain by reducing the value of Chinese company earnings when converted into dollars. The onshore Chinese currency is down 2.5% this month, while the offshore rate is 2.8% lower.

There is so far little sign that things will get better quickly. China blamed Washington for wrecking trade talks and insisted the U.S. must alter its “wrong practices” before negotiations can resume.

“China’s stance on the talks has been clear -- if the U.S. wants to resume talks, they should show sincerity and correct their wrong practices,” ministry spokesman Gao Feng said in Beijing on Thursday.

The same day, President Donald Trump described China’s Huawei Technologies Co. as "very dangerous," even as he said it could be included in some kind of trade deal with Beijing. His administration also proposed tariffs on goods from countries found to have undervalued currencies, which could broaden Trump’s trade salvos.

To contact the reporter on this story: Richard Frost in Hong Kong at rfrost4@bloomberg.net

To contact the editors responsible for this story: Sarah Wells at smcdonald23@bloomberg.net, Sofia Horta e Costa

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