Hollywood star Jason Momoa has urged world leaders to take serious actions on climate crisis in his United Nations (UN) speech.

He addressed the issue on September 27, reports aceshowbiz.com.

The actor and ocean activist spoke up for "all island nations" at the UN, and demanded more action from delegates, listing the issues that threaten some of the world's most beautiful places and claiming the people of the South Pacific, in particular, are suffering more, insisting they are at the "critical tipping point" of a crisis that could kill the planet.

"As a native Hawaiian born to a mother from Iowa, I have seen how one place can be oblivious to another," he said.

"The issues facing an island can feel so far removed from that place that is landlocked in the middle of our country. However, with a foothold in two worlds, I quickly began to see how a problem for one will soon become a problem for all...".

He added: "We, the island nations and all coastal communities, are the front lines in this environmental crisis. The oceans are in a state of emergency, entire marine ecosystems are vanishing with the warming of the seas, and as the waste of the world empties into our waters, we face the devastating crisis of plastic pollution."

Momoa said that "we are a disease that is infecting our planet".

He called on the leaders to honour the Paris Agreement and demand "global unity for a global crisis". Ironically, US President Donald Trump, pulled out of the Paris Agreement in 2017.

The actor ended his address by shouting "Ku Kia'i Mauna" to show his support for the Hawaiian activists fighting to stop the construction of a huge telescope on the sacred Mauna Kea mountain.

Momoa, who recently joined the protesters, later posted his speech on Instagram, adding the caption: "For those who couldn't watch it live, watch me fumble through my very honest and direct speech. No BS."