Environmental advocacy groups say the impact of overfishing on food stocks and biodiversity is an ecological threat comparable to climate change.

"There is a positive approach from civil society and the members of the WTO recognising that they could make a good case to show that the WTO, through trade, can help achieve broader environmental goals," Valles said.

"In general terms, there is acceptance that we should have prohibitions of certain forms of subsidies that contribute to overfishing."

Valles said WTO members were pushing for various exceptions to the subsidy bans and other proposals, and much work remained to be done to reach agreement on these.

In particular, developing countries are concerned at the impact of the new rules on small-scale artisanal fishermen, many of whom live in poverty.

TACKLE FISHING

Senior trade officials say the Doha round, launched in 2001, is close to a breakthrough. Ministers could be called next month to Geneva to clinch the outlines of a deal to open up world trade, intended to be concluded by the end of the year.

But on the core chapters of agriculture and industrial goods negotiators are hung up on a series of technical issues. The progress on fisheries is one of the more hopeful signs.

And it bodes well for forthcoming talks on climate change and growing interest in the impact of trade on the environment.

That said, the deal is not in the bag.

Banning operating subsidies on materials such as fuel, bait and ice, as proposed, would make many fishing fleets uneconomic.

The European Union is worried about the impact of a subsidies ban on fishing communities where there may be few other employment opportunities.

Countries such as Norway and Canada share those fears.

And the ban would certainly have an impact on the deep-sea fishing operations of China, South Korea and Japan, where fishing firms such as Maruha Nichiro Holdings and Nippon Suisan Kasha will be following the talks closely.

Advocacy group Oceana, which advises the US government, cites one recent study showing that one third of commercial fishing stocks are collapsing and all commercial stocks will be in collapse by the middle of this century.

Senior campaign director Courtney Sakai said subsidies were running at about $20 billion a year in an industry with sales of $80-100 billion -- a higher rate of subsidy than agriculture.

The key to tackling these subsidies was new trade rules.

"This is a major outcome that could come from the round that would benefit the environment and one of the most important commodities in the developing world," she said.

Those subsidies create an enormous incentive to overfish.

But Sakai said studies showed that stocks could rebound quickly within years if fishing is restricted.

Developing countries recognise the problem and the negotiations reflect intensive work done by Argentina and Brazil in particular.