Adds WuXi AppTec, analyst comments in paragraphs 10, 16-17

By Michael Martina and David Shepardson

WASHINGTON, June 8 (Reuters) - The U.S. on Monday issued an updated list of Chinese companies it believes are aiding Beijing's military, including e-commerce group Alibaba 9988.HK, Internet search provider Baidu 9888.HK and automaker BYD 002594.SZ.

The long-awaited update supersedes a list from early 2025, and comes less than a month after President Donald Trump met China's Xi Jinping on a visit to Beijing, where the two leaders maintained a delicate trade war truce.

In February, when Trump's trip to China had been pending, the Pentagon briefly posted an updated list, known as the 1260H or CMC list, but then quickly withdrew it with little explanation.

The new version released on Monday mirrors the withdrawn February list with the exception of the inclusion of China's top memory chipmakers CXMT and YMTC, two companies that had been removed from the short-lived February index to the ire of Washington's China hawks.

Other companies added include biotech firm WuXi AppTec 603259.SS, AI-driven robotics company RoboSense Technology Co Ltd 2498.HK and Unitree, a leading Chinese maker of humanoid and quadruped robots. On June 1, U.S. AI chipmaker Nvidia NVDA.O said it plans to work with Unitree to build robots for researchers.

China's embassy in Washington did not respond immediately to a request for comment.

Some companies, including two entities owned by Chinese state-owned oil major China National Offshore Oil Corporation (CNOOC) - CNOOC China Ltd and CNOOC International Trading - were removed. However, CNOOC subsidiary China BlueChemical Limited was added, and the department filing noted that CNOOC is directly controlled by China's government.

Companies can at times be taken off, not because the U.S. determines they aren't linked to China's military, but because they no longer operate in the U.S. or because an entity's name has changed.

Alibaba, Baidu, CXMT, YMTC, Unitree, CNOOC and Nvidia did not immediately respond to requests for comment.

A WuXi AppTec spokesperson told Reuters that the company's inclusion on the list was "clearly a mistake" and that it would take immediate actions to "correct this erroneous designation."

The listed firms "qualify for designation as 'Chinese military companies,'" and operate in the U.S., the Pentagon said in its filing, which is required at least annually under U.S. law. The companies can petition for removal, it added.

The list now includes a broad swathe of China's top technology firms key to advancing Beijing's military and industrial prowess, and its publication could inflame tensions between the rival countries, which are locked in an economic and geopolitical competition.

Though it does not formally impose sanctions on Chinese firms, under recent U.S. law the Defense Department will be prohibited starting later this month from contracting directly with companies on the list, and from buying their products or services via third parties beginning in 2027.

Those measures could have material costs for the Chinese firms and their partners.

Being added to the list also sends a potentially damaging message to Pentagon suppliers and other U.S. government agencies about the U.S. military's opinion of the firms, some of which have sued the U.S. over their inclusion.

Craig Singleton, a China expert at the Foundation for Defense of Democracies think tank in Washington, said the publication of the list served as a post Trump-Xi summit reality check on the heightened state of U.S.-China competition.

"Washington is no longer treating these as isolated companies. It is treating the entire technology stack as strategically contested," Singleton said.