Along with World Trade Organisation chief Pascal Lamy, the richest powers' top trade officials met with Brazilian Foreign Minister Celso Amorim for the latest of a long series of attempts to keep the WTO's ambitious goals on track.

After a vocal protest by about 50 anti-WTO activists, the four officials including US Trade Representative Rob Portman and EU Trade Commissioner Peter Mandelson headed into bilateral meetings and then dinner talks.

Before joining the meeting, which wraps up Saturday, Lamy said both rich and developing nations must make painful concessions if they are to fulfil their promise to enrich the lives of millions of people through freer trade.

"There is no time to lose," Lamy told Sao Paulo business leaders, noting that the WTO has only a month before it is meant to forge the outlines of a comprehensive agreement.

"On each of the three issues -- agricultural tariffs, industrial tariffs and domestic agricultural subsidies -- each of the big actors has to move," he said.

Lamy said the EU must lower its agricultural duties, the United States must cut domestic support for farmers and the G20 bloc of developing countries must open their markets to more industrial goods.

Brazil, with the backing of its G20 partners including India and South Africa, insists that the EU notably must first slash the generous trade protection afforded to its farmers.

But Mandelson, backed to an extent by Portman, retorts that developing nations must grant much greater access to industrial imports and service industries.

In an interview with Brazilian newspaper Valor Economico, Mandelson said the EU was committed to the April 30 deadline, "but we cannot take brutal short-cuts on complex questions".

The EU trade supremo said an offer by Brazil to halve its industrial tariffs was unacceptable to both Europe and the United States. Washington has to improve on its proposals to cut domestic farm support, he said.

Mandelson also said the WTO must not rush matters in a bid to forge a final agreement by the end of this year, before the US Congress regains the right to unpick any trade accord negotiated by the administration.