BRUSSELS, July 24 (Reuters) - The United States is considering putting its weight behind a project to speed the flow of gas across Ukraine to Europe, a senior U.S. official said on Thursday.

The project could add as much as 19 billion cubic metres of gas flow a year, equal to about two thirds the volume of the planned Nabucco pipline to Europe, U.S. Deputy Assistant Secretary of State Matthew Bryza told Reuters.

"In principle, we're very interested in doing this, if it's workable," Bryza said shortly before leaving for Ukrainian capital Kiev to discuss the plan.

"Now we are in the conceptual phase," he added. "We're just scoping it out... we'll have to look at feasibility studies and the possibilities of financing."

Ukraine is an important transit state for gas flows to Europe from Russia and Central Asian countries like Turkmenistan.

But regular disputes between Russia and Ukraine have prompted the European Union to seek new sources of energy or supply routes, such as the $12 billion Nabucco project.