"The success or failure of the round (of negotiations) will be decided in the 40 days before the end of April," Lamy told the European Parliament's international trade committee.

WTO negotiators are struggling to give fresh impetus to the Doha round of talks in the World Trade Organisation (WTO), launched in the Qatari capital in 2001 with the aim of boosting development in the world's poorest nations.

The clock is ticking towards an April 30 deadline for negotiators to resolve their differences over tariffs on agricultural products and industrial goods.

Lamy said that progress was possible only if the United States, the European Union and the so-called G20 group of emerging trade powers agreed to make compromises on issues dear to them.

"The US must move on domestic farm support, the EU must move on agriculture tariffs and the G20 must move on industrial tariffs," he said.

Although each side had already made some concessions, "the sum of the three offers is not enough," he said.