President-elect Donald Trump has said the United States should let China keep the navy unmanned underwater glider that it seized in the South China Sea.
"We should tell China that we don't want the drone they stole back - let them keep it!" Mr Trump tweeted a few hours after the US military announced it had reached an understanding with China for the return of the underwater glider.
According to the Pentagon, the drone was seized on Thursday while collecting unclassified scientific data in the South China Sea, which China claims virtually in its entirety.
The US demanded the drone back, calling it an "unlawful seizure" in international waters.
China said its military seized the underwater glider to ensure the safe navigation of passing ships, but would give it back.
It was not immediately known what effect, if any, the president-elect's tweet would have on the agreement with the Chinese.
The evening tweet was the second time Mr Trump injected himself into the controversy through Twitter on Saturday.
Misspelling "unprecedented", he tweeted on Saturday morning: "China steals United States Navy research drone in international waters - rips it out of water and takes it to China in unpresidented act." He later reissued the tweet, correcting the spelling.
Relations already were tense between the US and China following Mr Trump's decision to talk by phone with Taiwanese president Tsai Ing-wen on December 2. He later said he did not feel "bound by a one-China policy" regarding the status of Taiwan, unless the US could gain trade or other benefits from China.
China considers the self-governing island its own territory to be recovered by force if it deems necessary.
Meanwhile, Mr Trump told the final rally of his post-election tour that US first lady Michelle Obama "must have been talking about the past" when she said there was no sense of hope after his victory.
Mr Trump, speaking in Mobile, Alabama, then resisted escalating the spat further, suggesting "she made that statement not meaning it the way it came out".
But as he praised the Obamas for treating him so nicely when he visited the White House shortly after the election, many in the crowd booed the first family.
In an interview with Oprah Winfrey to be shown on Monday on CBS, Mrs Obama said she was now certain her husband's victory had inspired people because "now we're feeling what not having hope feels like".
"What do you give your kids if you can't give them hope?" she added.
Mr Trump's comments about the Obamas was one of the few conciliatory notes he sounded during a victory tour in which he showed few signs of turning the page from his blustery campaign to focus on uniting a divided nation a month before his inauguration.
At each stop, the Republican gloatingly recapped his election night triumph, reignited some old political feuds while starting some new ones, and did little to quiet the hate-filled chants of "Lock her up!" directed at Democratic rival Hillary Clinton.
At the tour's finale at the same football stadium in Mobile that hosted the biggest rally of his campaign, he saluted his supporters as true "patriots" and made little attempt to reach out to the more than half of the electorate that did not vote for him.
"We are really the people who love this country," he said.