The president previously attacked Greta Thunberg on Twitter with an apparently sarcastic message that called her a "very happy young girl"

Trump Again Attacks Teenage Climate Activist Greta Thunberg, Who Clapped Back at Him on Twitter Last Week

President Donald Trump is using his Twitter account to once again attack teenage climate activist Greta Thunberg, this time to amplify a snide dismissal of her public appearances as “acting.”

The commander-in-chief on Thursday jabbed at the Swedish 16-year-old: He retweeted and praised a Twitter user who criticized the passionate speech Thunberg gave at the U.N. Climate Action Summit in New York City late last month.

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A user by the name of @Opinion8dKellie shared video of Thunberg’s speech, in which the teen slammed world leaders for what she said was more interest in making money than in saving the planet by reducing carbon emissions.

“What an actress!” the user, @Opinion8dKellie, tweeted, adding, “I won’t be held hostage by someone who just got a learner’s permit. Sorry kiddo!”

Image zoom TIMOTHY A. CLARY/AFP/Getty; Win McNamee/Getty

Though the tweet was written on Sept. 23, Trump, 73, retweeted it Thursday morning.

“Keep up the great work Kellie!” he wrote.

In the original tweet, @Opinion8dKellie also referred dismissively to when a visibly aggrieved Thunberg said at the U.N.: “This is all wrong. I shouldn’t be up here. I should be back in school on the other side of the ocean. Yet you all come to us young people for hope. How dare you!”

RELATED VIDEO: Former Disney Star Skai Jackson Hopes Greta Thunberg ‘Doesn’t Get Intimated’ By the Haters

For her part, Thunberg wrote in a lengthy Facebook post in February that rumors that she was being “paid” or “used” to speak out on climate change were completely unfounded.

“I am absolutely independent and I only represent myself,” she wrote. “And I do what I do completely for free, I have not received any money or any promise of future payments in any form at all.”

The president is a noted climate change skeptic who has resisted large-scale solutions to what scientists describe as an escalating threat to the world. He has falsely claimed climate change was a hoax perpetuated by the Chinese.

The White House did not respond to PEOPLE’s request for comment about Trump’s continued attacks on Thunberg.

He previously shared footage of her speech on Twitter, adding an apparently sarcastic message: “She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!”

Thunberg took the dig in stride and even briefly changed her Twitter bio to reflect his words.

“A very happy young girl looking forward to a bright and wonderful future,” it read, according to screenshots, though she has since changed it once again.

In an interview with the Scandinavian talk show Skavlan, Thunberg said she interpreted Trump’s words as sarcastic but said that “of course” he would write something like that.

“I mean, you can interpret it in many different ways,” she said. “But I mean, I knew that sometime he was probably going to say something about me. It was like, it doesn’t make any difference, in a way.”

She and Trump also shared a brief but memorable moment at the summit when Thunberg gave him an apparently icy stare that was caught on video.

Image zoom Greta Thunberg Greta Thunberg/Twitter

Thunberg later clarified on Skavlan that the look actually just came because she was surprised by Trump’s appearance.

“I was stopped because suddenly he came in and security went, ‘You have to step to the side.’ And I just wondered what was going on,” she said. “And then he showed up. I think I was very shocked.”

Regardless of internet criticism from Trump and others, Thunberg has repeatedly brushed off hateful attacks.

“I honestly don’t understand why adults would choose to spend their time mocking and threatening teenagers and children for promoting science, when they could do something good instead,” she wrote on Twitter on Sept. 25. “I guess they must simply feel so threatened by us.”

Image zoom Greta Thunberg LIONEL BONAVENTURE/AFP/Getty

She added, “But don’t waste your time giving them any more attention. The world is waking up. Change is coming whether they like it or not. See you in the streets this Friday!”

She’s even changed her Twitter bio to reflect her sense of humor: “A kind but poorly informed teenager,” it reads.