Story highlights China said the US had "hyped up" the issue

Trump called China's action "unprecedented"

Washington (CNN) China has agreed to return the US underwater drone that it seized in international waters earlier this week, the Pentagon said Saturday.

"We have registered our objection to China's unlawful seizure of a US unmanned underwater vehicle operating in international waters in the South China Sea. Through direct engagement with Chinese authorities, we have secured an understanding that the Chinese will return the UUV to the United States," Pentagon spokesman Peter Cook said in a statement.

Details were not immediately available on when or how the drone may be returned.

Earlier, China's Defense Ministry said authorities had decided to return it, but criticized the US for having "hyped up" the issue. President-elect Donald Trump weighed in on the incident, calling China's action "unprecedented."

We should tell China that we don't want the drone they stole back.- let them keep it! — Donald J. Trump (@realDonaldTrump) December 18, 2016

Later in the day, he tweeted, "We should tell China that we don't want the drone they stole back.- let them keep it!"

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