UN member states agreed Saturday to begin negotiations on a treaty to protect marine biodiversity in ocean areas extending beyond territorial waters, in a move heralded by environmental organizations.

The eventual UN treaty would be the first to specifically address protection of marine life, calling for the preservation of vast areas threatened by pollution, overfishing and global warming.

The agreement was made after four days of discussions in New York, and still must be approved by the UN General Assembly by September, with a treaty appearing at the earliest in 2018.

But the agreement was reached only after a small group of countries engaged in fishing and ocean mining blocked a more rapid time line during the discussions between experts from the 193 member countries.

A majority of nations called for quick action but several countries such as the United States, Russia, Canada, Iceland and Japan expressed reluctance.

The treaty represents international zones that make up 64 percent of the world's oceans or a total of 43 percent of Earth's surface.

"This is the biggest biosphere on earth and there is no legal instrument in place to establish national parks at sea to protect marine life," Karen Sack of the Pew Charitable Trusts told AFP.

"Today's agreement could go a long way in securing the protection the high seas desperately need," Greenpeace's Sofia Tsenikli said in a statement.

In addition to its role regulating the climate, the ocean is a source of protein to some 3 billion people.

According to the agreement's text, a preparatory committee will begin outlining a treaty in 2016 and make recommendations to the General Assembly at its September 2017 session.

The treaty would concern "conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction," creating in particular, "marine protected areas" and sharing of benefits derived from the deep sea, such as marine genetic resources, the text said.

The UN has been in discussions on the matter for 10 years, but the General Assembly pushed for action following the Rio+20 conference on Earth's environmental problems and enduring poverty in 2012.