(Bloomberg) — Chinese stocks slid suddenly on Tuesday before the second day of trade talks with the US, showing that investors remain on edge as the world’s two largest economies seek to address some contentious issues.

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A gauge of Chinese shares in Hong Kong (^HSCE) fell as much as 0.9% as trading resumed after the mid-day break, and finished the session down 0.2%. It had risen as much as 0.5% earlier. The CSI 300 Index (000300.SS), a benchmark for onshore equities, flipped to a loss to end 0.5% lower. US equity futures also retreated from the day’s high.

It wasn’t immediately clear what caused the sudden declines. Some investors pointed to an earlier commentary listed in a social media account affiliated with state broadcaster CCTV, which said that “the US should realistically view the progress made and revoke negative measures against China.” Beijing is earnest about trade talks with the US but is at the same time principled, it added.

“The market is too sensitive,” said Fu Shifeng, investment director at Cheng Zhou Investment. “People seem to be speculating that the talks didn’t go well.”

Hopes that trade talks will help ease Sino-American tensions and pave the way for a potential deal between the two nations have spurred a sharp rebound in Chinese shares in recent weeks. The Hang Seng China Enterprises Index (^HSCE) entered a bull market on Monday, taking its gains from a April low to over 20%.

Global investor sentiment toward China is improving, with increased willingness to add positions in Chinese equities and greater conviction in the “new consumption” and tech spaces, Morgan Stanley analysts including Laura Wang wrote in a recent note.

Representatives from both nations are slated to meet again on Tuesday at 10 a.m. local time in London. Trump on Monday had told reporters that the US was “doing well with China” and that he was “only getting good reports.”

The first round of negotiations since delegations from the countries met a month ago is aimed at restoring confidence that both sides are living up to commitments made in Geneva. During those discussions, Washington and Beijing agreed to lower crippling tariffs for 90 days to allow time to address a trade imbalance that the Trump administration blames on an unfair playing field.