By Doug Palmer

WASHINGTON, April 8 (Reuters) - Negotiators in world trade talks have made "a lot of progress" over the past three months and are close to a possible breakthrough, a top U.S. trade official said on Tuesday.

"Our hope is that ministers will be able to meet very soon -- this spring -- to reach an agreement that we can credibly say will open new markets by cutting tariffs," Deputy U.S. Trade Representative John Veroneau told the President's Export Council, a White House advisory group.

"We're at a point now where hopefully we can have a breakthrough," Veroneau said. "We've made a lot of progress over the past three months in Geneva and in capitals."

The United States and other members of World Trade Organization launched the Doha round of world trade talks more than six years ago with the goal of finishing by January 2005.

The talks have been plagued over deep differences over how much to cut rich-country farm subsidies, as well as tariffs on agricultural and manufactured goods in both developed and advanced developing countries.

WTO Director Pascal Lamy said on Tuesday he could call a meeting of trade ministers in May to try to strike a broad deal. That would be followed by further talks to fill in details.

"All the material is already on the table. It just remains for us to find a final compromise," Lamy told reporters at a breakfast briefing in Paris.

Veroneau said negotiators were whittling down the number of issues for trade ministers to decide, but the next four to eight weeks were critical to the success of the talks.

"President Bush made clear that he is prepared to make difficult choices on agriculture, but it requires others to step forward to cut tariffs," Veroneau said.

Joe Glauber, Washington's senior agriculture negotiator in the Doha round, said on Monday countries were "very, very close" in difficult technical negotiations over opening import markets for politically sensitive farm goods.

Washington has insisted the deal must create significant new export opportunities for U.S. farmers, manufacturers and service providers in order to persuade Congress to approve deep cuts in farm subsidies.

Even so, many U.S. service industry companies are concerned they could be left out of the deal because the talks have mostly focused on agriculture and manufacturing.

Services ranging from banking to telecommunications to express delivery account for about 70 percent of the U.S. economy but only about 30 percent of U.S. exports.

Veroneau told the Export Council the United States should insist on a strong services component in any Doha deal.

Services "represent an incredible opportunity for us globally and those have to be part of the agreement," he said.