* Lamy says revising agenda "horribly complex"
* Deal technically possible but needs political will
* U.S. farm negotiator says bilaterals must continue (Adds U.S. chief farm negotiator's comments)
By Helen Popper and Maximilian Heath
PUNTA DEL ESTE, Uruguay, April 20 (Reuters) - The head of the World Trade Organization rejected proposals to revise the Doha trade agenda on Tuesday, saying changes could be unpopular with developing nations seeking to open up world commerce.
European Union trade chief Karel de Gucht was quoted as saying last week that the goal of the long-running Doha round should be revised to either seek a "Doha light" deal or aim for a more ambitious outcome.
However, WTO Director-General Pascal Lamy told reporters revising the agenda would be "horribly complex, plus probably politically unpalatable for developing countries who want this round to resolve a fairer system of rules for them."
Lamy said none of the WTO's 153 members had suggested revising the Doha agenda during a stock-taking exercise in March during which they tacitly dropped a deadline for a trade liberalization agreement.
The Doha round was launched in the capital city of Qatar in late 2001 with the goal of helping countries prosper through trade. But negotiators have missed every deadline set by themselves or political leaders for finishing the round.
At the height of the global economic slowdown, the G20 group of major world economies called on trade ministers to reach a deal this year, but the political will to close stubborn gaps between rich and poor countries and importers and exporters has been lacking.
Lamy was in Uruguay for a meeting of the Cairns Group of agricultural exporting countries, which hopes to inject new life into the Doha round.
"My sense is that (the Cairns Group meeting) will send a signal of political energy mobilization. That's what they're after," Lamy said.
He reiterated that a deal to end the 9-year-old round is technically possible as long as world leaders show political will.
REMAINING DIFFERENCES
Lamy estimates nearly 80 percent of the issues in the negotiations have been resolved.
But the slow progress in bridging the remaining differences has fueled suggestions the talks be paused for a while or scrapped altogether to focus on other trade areas.
Much of the impasse comes from Washington's demand that major developing countries make better offers to open their farm, manufacturing and services markets in exchange for U.S. cuts in farm subsidies and politically sensitive tariffs.
In an effort to gain more market access, the United States has been holding bilateral talks with China, India and Brazil.
Chief U.S. farm trade negotiator Isi Siddiqui said those talks should be maintained with an eye to a broader deal.
"We have had some success but I think this dialogue needs to continue," he told Reuters. "That doesn't mean in any way that we're abandoning the multilateral discussions."
Siddiqui, on his first trip since taking office in March, acknowledged the frustration expressed by farmers and ministers during the Uruguay meeting over the lack of progress.
"I think frustration is not particular to the Cairns Group ... I see the same thing in the U.S. sector, which cannot do business in India or cannot export to other countries because of high tariffs," he said.
"We want to level the playing field, but I think it's very difficult for a farmer to understand why it's taking so long, so I can understand."
(Editing by Bill Trott)