Washington, Aug 22 : Democratic presidential hopeful Barack Obama has announced that he has decided on a running mate, but declined to provide a name, fanning already intense speculation about the choice.

"I've made the selection, and that's all you're going to get," Senator Obama told reporters during a stop at Virginia Favorites Ltd., a peanut and gift shop in Emporia.

Obama is expected to announce his vice presidential decision by Saturday. His campaign has scheduled a joint appearance in Springfield, Ill., where he announced his presidential bid more than a year and a half earlier, The Washington Post reported.

It is unclear whether Obama and his vice presidential choice will travel together from there. Earlier in the campaign, advisers suggested it was likely that the running mate would travel apart from the presumptive nominee for a little bit before making a separate arrival at the Democratic National Convention in Denver.

The Obama campaign also joined with the campaign of Senator John McCain in announcing that the two candidates will appear in three debates on September 26 in Oxford, on October 7 in Nashville; and on October 15 in Hempstead. A vice presidential debate is scheduled for October 2 in St. Louis.

The first presidential debate will focus on foreign policy and national security. The second will have a town hall format with questions coming from the audience and online, and the third will center on the economy and other domestic issues.

ANI