However, Blair said that he was more optimistic than before.

"I'm not saying it's going to happen, but I am more optimistic than I was," Blair told his monthly press conference in London. "There is an appreciation now of how important this is."

Blair said a deal would do "an immense amount for the health of the world economy".

He said his rising optimism was based on intensive talks worldwide, including in Washington involving US President George W. Bush, the European Commission and German Chancellor Angela Merkel as well as those with Brazilians, Indians and others.

He said much of his work schedule was devoted to efforts toward a deal because "next few weeks, I think, will be particiuarly crucial".

The WTO suspended the round in July last year after negotiators failed to reach agreement after five years of talks.

The round, launched in the Qatari capital in November 2001, is in an impasse as Western and developing countries remain split on issues such as agricultural subsidies and market access.

Developing countries want lower tariffs on their agricultural exports to US and European markets while industrialised nations seek greater access to developing and emerging nations for their industrial services and goods.