Democratic officials said Thursday that Mr. Clinton will give a speech on the third night of the convention, before an address by the as-yet-to-be-named running mate for, the party's likely presidential nominee. The officials spoke on condition of anonymity before the details were formally announced.
Exactly what role the former president would play at the gathering Aug. 25-28 has been the subject of speculation since his wife, New York Sen. Hillary Rodham Clinton, ended her bid for the Democratic presidential nomination in early June and endorsed Obama.
Obama clinched the nomination after a sometimes bitter primary contest with Clinton.
Sen. Clinton is expected to speak on the convention's second night.
Earlier Thursday, Obama dismissed suggestions that tension between his supporters and hers could upset the gathering.
Obama told reporters that their staffs were working out mutually agreeable convention logistics. At the same time, Clinton was assuring her supporters during an online chat that she and Obama were "working together to make sure it's a big success."
Neither answered questions about whether Clinton's name should be placed in nomination so that her backers could record their votes.
Amid reports that some Clinton backers hope to raise her profile at the convention or even continue to push her candidacy, Clinton and Obama were publicly trying to ease the strained relations that exist between some of their supporters.
Flying home to Chicago, Obama told reporters that he had talked separately this week to Clinton and her husband, and that they were enthusiastic about having a smooth convention.
"As is true in all conventions, we're still working out the mechanics, the coordination," Obama said. One such issue is whether there will be a convention roll call on Clinton's nomination, he said.
"I'm letting our respective teams work out details," he said. Asked if that meant he wouldn't object to her name being placed in nomination and a vote taken, Obama said: "I didn't say that. I said that they're working it out."
Clinton has not said whether she will seek a formal vote on her bid for the nomination.
During the online chat on her Web site, she wrote that she and Obama will ensure Democrats are "fully unified."
Clinton was expected to deliver a prime-time address to delegates on Aug. 26, the second night of the convention. With the delegate roll call planned for the next evening, Obama was set to accept the nomination with a speech on the convention's fourth and final night.
"We will ensure that the voices of everyone who participated in this historic process are respected and our party is fully unified heading into the November election," Clinton wrote. "While no decisions have been made yet, I will make sure that we keep you up to date and involved with all of the convention activity."
Obama was asked whether allowing Clinton's name to be placed in nomination might lead to a catharsis for the party.
"I don't think we're looking for catharsis. I think what we're looking for is energy and excitement," he said.
Clinton insisted during the Web chat that she was sincerely behind Obama after someone asked whether she truly was supporting him or was "just saying what you have to?"
Another questioner wanted to know if there was any possibility her name would be placed in nomination, arguing that doing so "would at least give your supporters a voice in the choice for the party's nominee." She was noncommittal.
Someone else posted a note saying he hopes Clinton becomes Obama's running mate. In her response, Clinton repeated that she will do whatever Obama asks of her but it is his decision "and I am going to respect the privacy of that process by not discussing it."
The Clintons' stance toward Obama's candidacy is being closely scrutinized as the convention nears - particularly after remarks by Bill Clinton earlier this week during a trip to Africa. Asked whether Obama was prepared to become president, the former president replied, "You can argue that nobody is ready to be president," and said he himself learned a lot in his first year on the job.
The remark was widely viewed as tepid and unenthusiastic, particularly in light of Republican candidatefrequent criticism that Obama is not ready to be president.