The long running round of Doha world trade talks could finally run out of steam in 2011 if no deal is reached, the European Union's top trade official said on Thursday.

I fully believe if we do not manage to get a deal done next year, there is a very big risk Doha will never get done, EU Trade Commissioner Karel De Gucht said in remarks at the Peterson Institute for International Economics.

But De Gucht, who is Washington for talks with U.S. officials, said he was personally optimistic a deal could be struck.

The Doha round was launched nine years ago with the goal of opening up markets around the world to help developing countries prosper.

However, countries have been stuck over formulas for cutting agricultural farm subsidies and tariffs and making comparable market openings for manufactured goods and services.

De Gucht said he was more optimistic about the United States' interest in finishing a deal after last month's U.S.-EU summit in Lisbon.

There is a short window of opportunity in the next six or eight months to pull things together, but it will require give and take from all the key players, he said.

(Reporting by Doug Palmer; Editing by Jackie Frank)