Kerry urges global strategy to save the world's oceans

US Secretary of State John Kerry Monday called for a global strategy to save the world's oceans, saying everyone had a "shared responsibility" to protect the seas covering 75 percent of the planet.

"Let's develop a plan" to combat over-fishing, climate change and pollution, Kerry urged as he opened a ground-breaking two-day conference of world leaders, scientists and industry captains.

He warned that there were already 500 "dead zones" around the world where marine life can no longer be sustained, adding that a third of the world's fish stocks were also "overexploited."

Heads of government and state as well as ministers from some 80 countries are gathering with researchers and experts from the fishing, plastics and farming industries for the conference at the State Department.

"No-one should mistake that the protection of our oceans is a vital security issue," Kerry told the conference opening.

"The ocean today supports the livelihoods of up to 12 percent of the world's population. It is also essential to maintaining the environment in which we all live," Kerry said.

Protecting the oceans was also essential for food security, Kerry stressed saying some three billion people "depend on fish as a significant source of protein."

He urged everyone to come together to develop concrete action plans to tackle the different threats posed to the ocean, and said US President Barack Obama would have an announcement to make on extending America's marine conservation areas.