* US trade negotiator sees "no shortcut" to Doha deal
* Siddiqui cites meaningful progress in past six months
WASHINGTON, Oct 5 (Reuters) - A top U.S trade official indicated on Tuesday that the long-running Doha round of world trade talks could stretch into 2012, but said some progress had been made over the past six months.
"The U.S. view is that there is no shortcut to a Doha success," U.S. chief agricultural trade negotiator Isi Siddiqui said in the prepared text of a speech given in Brussels, a copy of which was released in Washington.
"Deadlines won't do it, mandated formal processes won't do it, and attempts at high-level 'Big Bang' political events won't do it," Siddiqui told a European farm policy audience.
Siddiqui repeated the U.S. demand that major developing countries such as China, India and Brazil make better offers to open their markets to more imported goods and services.
He also warned that Congress has already began work on a new farm bill that will govern U.S. crop subsidy programs after the current farm bill expires in 2012.
Siddiqui indicated that the Doha negotiations might run into 2012, saying that if there is no deal by then, the United States would be free to continue spending at limits allowed under the current WTO pact.
"Unless a Doha deal is reached between now and the autumn of 2012, the next farm bill will have as its guidepost our current Uruguay Round commitments," he said.
The Doha round was launched nearly nine years ago with the goal of helping poor countries prosper through trade. The talks collapsed most recently in July 2008 and have struggled to get on their feet ever since.
Countries remain at odds over formulas for cutting farm subsidies in rich countries such as the United States and the European Union in exchange for cuts in agricultural tariffs in both developed and developing countries.
Disagreements over various proposals for opening manufactured goods and services markets around the world to more trade also plague the talks.
Siddiqui said negotiators "have made meaningful progress in the Doha negotiations over the past six months" dealing with a number of technical issues.
"The challenge in the months ahead will be to move successfully from process to substance," he said.
WTO Director General Pascal Lamy, who will be in Washington this week for meetings at the International Monetary Fund, has said he hopes a Group of 20 nation summit in South Korea in November will give new momentum to the Doha talks.
(Reporting by Doug Palmer; Editing by Will Dunham)