The United Nations is keen to rope in K-pop stars to promote good causes among their legions of teenage fans.

The UN has repeatedly invited boy band Bangtan Boys, also known as BTS, to deliver speeches on major global issues, and on Tuesday girl band Aespa addressed this year's High-level Political Forum on Sustainable Development in New York.

"The topic of sustainable development is urgent and we believe the next generation must support sustainable development goals in order to protect the world that we live in," Aespa member Giselle said. They also played a music video of their hit "Next Level."

This is the fifth time the global body has invited K-pop groups. BTS gave speeches at the UN General Assembly three times, in 2018, 2020 and 2021, and last year, girl band Blackpink were appointed as UN SDGs ambassadors.

Girl group Aespa give a speech at the UN General Assembly in New York on Tuesday.

Normally it is Hollywood stars like Leonardo DiCaprio and Emma Watson as well as singers like Stevie Wonder who speak at the UN, but BTS was the first Asian act to do so.

Their main attraction is their global teenage fanbase. When BTS delivered a speech at last year's UN General Assembly, around 980,000 people watched the event live on YouTube, while a clip of their performance of "Permission to Dance" afterwards has been viewed 69.39 million times.

UN Secretary-General Antonio Guterres thanked them for attracting global attention to environmental causes and admitted he would not be able to make them go viral as BTS can.

Bangtan Boys pose at the UN General Assembly in New York on Sept. 20, 2021.

K-pop fans dutifully embrace their messages, from the fight against racism and poverty to gender equality.

In 2020, BTS' fan club, the Army, posted hashtags and collected donations to support the Black Lives Matter movement, while Blackpink's fan club Blink supported the pro-democracy movement in Peru and anti-terrorism. U.S. media have labeled the phenomenon "K-pop activism."