BERLIN (Reuters) – Key members of the World Trade Organisation (WTO) only have a few weeks to strike a deal in the current round of global trade talks, U.S. Agriculture Secretary Mike Johanns said on Tuesday.

"We really need to see this agreement coming together here in the next six weeks or so for the work to be done, to have this in shape for the end of 2006," Johanns told reporters in the German capital, where he is trying to break a U.S.-European Union impasse on issues like farm subsidies.

Last week six of the world's top trading powers made little headway at a meeting in London aimed at removing long-standing hurdles to a global trade deal, but reaffirmed a commitment to conclude a key part of the pact by the end of April.

The WTO's 149 member states are racing to meet the April deadline they set in Hong Kong last December for a draft accord in agriculture and industrial goods, two of the most contentious areas of the overall free trade negotiations.

The WTO's Doha round, launched in 2001 with the aim of boosting the global economy and lifting millions out of poverty, must be wrapped up by early next year. "The round, in my judgment, has got great potential," Johanns said. "I remain optimistic about the round but it also faces great challenges."

Johanns said it would not be possible to extend the self-imposed deadline.

Several deadlines for the Doha round have already been missed but negotiators say it risks complete collapse without a speedy agreement because U.S. President George W. Bush loses "fast-track" powers to approve trade deals in mid-2007.

Both the United States and the European Union are under pressure to make more concessions in agriculture, where many poorer countries feel they have most to gain from freer trade.

Washington is being urged to go beyond its offer to slash farm subsidies by up to 60 percent, which critics say lowers budget ceilings but without cutting actual spending. The EU faces demands for deeper tariff cuts to open up its highly protected farm market.

In turn, rich nations are insisting that leading developing states such as Brazil and India do more to open their industrial and services markets to imports.

Johanns gave no details about what he would tell German officials during his visit to Berlin.