"Our ocean has been under pressure for decades. We can no longer ignore the ocean emergency," UN Secretary General Guterres said in a message read to negotiators.
"The impacts of climate change, biodiversity loss and pollution are being keenly felt around the globe, affecting our environment, our livelihoods and our lives," he added.
The UN leader also said "In adopting a robust and ambitious agreement at this meeting, you can take an important step forward in countering these destructive trends and advancing ocean health for generations to come."
After 15 years of formal and informal talks, delegates have been meeting in New York since February 20 to discuss a text that aims to protect nearly half the planet.
It is the third "final" negotiating round in less than a year and it's due to end Friday. Observers who spoke with AFP were optimistic that the treaty will get hammered out.
The high seas begin at the border of countries' exclusive economic zones, which extend up to 370 kilometers from coastlines. They thus fall under the jurisdiction of no country.
While the high seas comprise more than 60 percent of the world's oceans and nearly half the planet's surface, they have long drawn far less attention than coastal waters and a few iconic species.
"With flexibility and perseverance, you can secure an outcome to help ensure our ocean will be healthier, more resilient and more productive, benefiting our planet and humankind," said Guterres.
