The US has rejected a proposed merger between the Chicago Stock Exchange and a Chinese-linked investor group.
The decision comes after more than two years of reviews by officials.
The tie-up was initially approved by the Committee on Foreign Investment in the United States, pending further approval by the Securities and Exchange Commission (SEC).
But US politicians, including President Trump, have said letting a Chinese firm invest in a US exchange was a bad idea.
Under the proposal, the Chinese-led North America Casin Holdings group would have bought CHX Holdings, which owns the Chicago Stock Exchange.
The exchange, which handles just 0.5% of US stock trades, had said the deal would have provided the exchange with "vital capital".
That funding would have been used "to boost numerous initiatives designed to benefit the city of Chicago, the US economy and market structure as a whole".
While the investment got an initial vote of approval by SEC staff in August 2017, the commission ultimately ruled that the deal did not meet the rules that govern US stock exchanges.
"The review process has also raised questions about whether the proposed ownership structure will allow the commission to exercise sufficient oversight of the exchange" the SEC said on Thursday.
The SEC's decision follows several other moves by US officials to deter Chinese firms doing business in the US, or partnering up with US firms to sell their goods in the country.
In January, China's telecommunications giant Huawei said it had been unable to strike a deal to sell its new smartphones via a US carrier, widely reported to be AT&T.
Also earlier this year, the US also blocked a $1.2bn (£880m) sale of money transfer firm Moneygram to China's Ant Financial, the digital payments arm of Alibaba.
It was the highest profile Chinese deal to be rejected by Washington since Donald Trump came to power.
US politicians who had opposed the stock exchange deal said they applauded the decision.
"This has been a long fight, and I'm grateful we now have a president who recognises the national security threats of allowing a Chinese government-affiliated company to own the Chicago Stock Exchange," Republican congressman Robert Pittenger said in a statement.