By Susan Heavey and Michael Martina

WASHINGTON (Reuters) -The Biden administration on Tuesday gave investors two extra weeks to buy or sell securities in certain companies it deems are tied to the Chinese military, an extension it said was needed to craft a stronger policy to prohibit such trades.

President Joe Biden’s administration has been reviewing a number of aspects of U.S.-China policy, including a ban imposed under his predecessor Donald Trump on investments in certain Chinese companies that the United States says are linked to China’s armed forces and intelligence agencies.

Investors now have until 9:30 a.m. (1330 GMT) on June 11 to compete their transactions, the U.S. Treasury Department said in a notice posted on its website. The previous deadline was May 27.

A senior administration official said the White House was deeply concerned about the issue, and that the two-week extension would allow it to address problems in the Trump administration’s executive order, which was drafted and implemented in a “careless manner.”

The new policies, once complete, would “strengthen our ability to prohibit U.S. investment in the PRC’s military, intelligence, and other security apparatuses,” the official said, using an acronym for the People’s Republic of China.

“We will have more on the permanent way forward soon, and we are determined to deal with this issue expeditiously,” the official said.

A request for comment from the Chinese consulate was not immediately returned.

At least eight Chinese companies have been placed under such restrictions. One, mobile phone maker Xiaomi , filed a lawsuit in response, and the U.S. Defense Department agreed to remove it from the banned list.

In March, a federal judge had temporarily blocked enforcement of the Xiaomi blacklisting, citing the U.S. government’s “deeply flawed” process for including it in the ban. The judge later also suspended an investment ban imposed on Luokung Technology Corp , a Chinese mapping technology company.

Xiaomi was among the more high-profile Chinese technology companies that Trump targeted for alleged ties to China’s military.

Smartphone rival and telecommunications equipment maker Huawei Technologies Co Ltd [HWT.UL] was also put on an export blacklist in 2019 and barred from accessing critical technology of U.S. origin, affecting its ability to design its own chips and source components from outside vendors.

The measures effectively crippled the company’s smartphone division.

The U.S. Department of Defense also placed similar restrictions on China’s Semiconductor Manufacturing International Corporation, a firm key to China’s national drive to boost its domestic chip sector.

(Reporting by Michael Martina, Susan Heavey and Trevor Hunnicutt in WashingtonEditing by Peter Graff and Aurora Ellis)

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