WASHINGTON, D.C. -- U.S. military conversations continue with China to gain the return of an unmanned underwater drone that was seized by the Chinese Navy last week, the Pentagon said Monday.

Pentagon press secretary Peter Cook said that U.S. and Chinese officials, including military leaders, are working out the logistical details of the exchange. He provided no other specifics.

A Defense Department official tells CBS News correspondent Adriana Diaz the plan is to return the drone in the South China Sea, near the contested Scarborough Shoal. The hand-off should happen by 6 a.m. ET.

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The drone should be returned by the same PRC Navy ship that took it, but it will not go back to the Bowditch, Diaz reported.



Cook said the drone was seized illegally by the Chinese, and the U.S. is working to get it returned as quickly as possible.

The drone was being operated by civilian contractors collecting unclassified scientific data in international waters in the South China Sea near the Philippines. The USNS Bowditch, which is not a combat ship, was recovering two of the gliders when a Chinese ship approached, launched a small boat and picked up one of the drones, the Pentagon said.

State Department spokesman for East Asia and the Pacific, Justin Higgins, said Monday the seizure of the underwater drone was “unacceptable” and without basis in international law.

“China’s seizure of a U.S. unmanned underwater vehicle (UUV) operating lawfully and in plain sight of a U.S. Navy vessel was unacceptable. China’s action had no basis under international law,” Higgins said.

Higgins said China informed U.S. ambassador to China, Max Baucus, on Saturday morning at approximately 3:30 a.m. EST that China would return the drone.

President-elect Donald Trump summarized the incident Saturday, tweeting: “China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unprecedented act.”

China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unprecedented act. — Donald J. Trump (@realDonaldTrump) December 17, 2016

After both the U.S. and China agreed the drone would be returned, Mr. Trump’s comments breathed new life into an incident that both militaries seem eager to put behind them, CBS News correspondent Adriana Diaz reported.

Chinese state media delivered a statement from its military this weekend that was laced with annoyance. It said China would return the drone because it posed no safety threat, but added that the U.S. has unilaterally and inappropriately hyped the issue.

Hours later, Mr. Trump, while in Alabama for his victory tour Saturday, launched two tweets at China. The most recent said: “We should tell China that we don’t want the drone they stole back.- let them keep it!”

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

China didn’t appreciate the comment.

“We don’t like the word steal. That’s totally inaccurate,” China’s foreign ministry spokeswoman Hua Chunying said. “The Chinese navy found the device and examined it in a professional manner … It’s as if you saw something on the street and someone asked you for it, you’d have to examine if it really belongs to them.”



An editorial in the state-run tabloid, The Global Times, went further, issuing a threat. It said if Mr. Trump “treats China after assuming office in the same way as in his tweets, China will not exercise restraint.”

The incident played out at the center of one of the most sensitive issues between the U.S. and China: the South China Sea. Six countries claim parts of the sea, but China declares nearly all of it is theirs. Recent satellite images also show China installing weapons on artificial islands it built there to defend its claim.

Further complicating the matter is that the drone appeared to be seized outside of China’s self-proclaimed jurisdiction. A U.S. defense official said the drone will be returned in a boat-to-boat transfer. The timing is still unclear but we’re told the hand off may be delayed by weather.