World Trade Organisation negotiations aimed at reducing barriers to global commerce have gone nowhere for the past six years, with differences, notably on trade in agricultural products, blocking progress in the Doha Development Round, launched with great fanfare in the Qatari capital in 2001.

Blair warned on Monday that the international community was running out of time.

"If we do not do a deal, if it falls away, then I think the impact will be bigger than people think," he said.

"It will be a blow to multilateralism, not good for international trade and it will indicate that protectionism is on the rise again.

"If we do not get this done -- the headline agreement -- in the next two to three weeks, then I think it will be very hard to see how we will get a deal."

Blair, who will quit office on June 27, insisted he was doing "literally everything I can" to try to secure a deal and was in regular talks with other leaders.

On Saturday, finance ministers from the Group of Eight industrialised powers called for agreement on the Doha round "as soon as possible."

Britain's finance minister Gordon Brown, will take over from Blair as prime minister in just over five weeks' time.

Trade negotiators are under pressure from a key date, June 30, when US President George W. Bush's "fast track" trade authority expires. Under current legislation, the US Congress is entitled to approve or reject trade deals signed by the administration but cannot amend them.

Without "fast track," a Doha Round trade liberalisation accord approved by the US administration could be in danger of being picked apart -- and neutralised -- by members of Congress.