"Hong Kong has flourished as a bastion of liberty," Pompeo said in a statement. "The United States strongly urges Beijing to reconsider its disastrous proposal, abide by its international obligations, and respect Hong Kong's high degree of autonomy, democratic institutions and civil liberties, which are key to preserving its special status under U.S. law."
China is eager to pass a law that would ban "treason, secession, sedition and subversion" in Hong Kong.
Critics claim the law would strip the city of the rights it currently enjoys because of its semi-autonomous status.
White House economic adviser Kevin Hassett said China risked a major flight of capital from Hong Kong that would end the territory's status as the financial hub of Asia.
Pompeo and Hassett's comments aren't likely to sit well with Chinese President Xi Jinping or the ruling Communist Party, which have had a prickly relationship with the United States that has further been strained over trade disputes and the global coronavirus pandemic.
Beijing has been hellbent on pushing the measure through and claims "law-based and forceful measures" must be in place to "prevent, stop and punish" protests in the future.
Hong Kong was required to introduce security legislation after the handover from British control to China in 1997.
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While the United States has limited leverage with China over Hong Kong, it could be cut off if the Trump administration determines that the Sino-British Joint Declaration, which was supposed to give the territory 50 years of special status after it reverted to Chinese rule, has been violated.
During an interview on Fox Business Network on Friday, Hassett claimed the damage that would come from China's proposal would be mostly self-inflicted.
“They’re going to see a lot of economic harm from what they’re doing,” he said, adding that businesses would not want to invest or keep money “in a place where they’re basically sneering at the rule of law.”
“And so, I would expect that they’re going to have serious capital flight problems,” Hassett said. “And Hong Kong, if they follow through this, will no longer be the financial center of Asia, and they themselves will bear very, very heavy costs.”
The Associated Press contributed to this report.