"We've had very positive discussions and we've reached some significant agreements," said David Bonior, the former Michigan congressman who is brokering the discussions.
But Bonior stressed that significant hurdles remain as leaders work out how a unified labor federation would be structured and what its goals would be.
Seven unions, led by the Service Employees International Union, bolted from the AFL-CIO in 2005. They complained the federation focused too much on political campaigns and not enough on recruiting new members. The break reflected frustration with steadily declining union membership, from a peak of 35 percent of the work force in the 1950s to about 12 percent today.
But now the political landscape has changed with Democrats taking the White House and control of Congress. Union officials see a window of opportunity to accomplish key goals, including passage of legislation that would make it easier for workers to organize unions.
"There's obvious benefits in terms of efficiency, message delivery, financial savings and a host of other reasons," Bonior said. "You can always be more effective if you're talking in one house as opposed to three."
Talks have included the 3.2 million-member National Education Association, the nation's largest union, which was not previously aligned with either federation but could become part of the new structure.
None of the leaders involved has publicly talked about specifics, but the pace of negotiations has picked up. The issue is prominent on the agenda during the AFL-CIO's annual winter meeting in Miami next week.
"We are still talking," Change to Win chairwoman Anna Burger told reporters recently.
Still, there are major issues to resolve, including who would lead the new federation, how organizing should be done and even what coalition would be called.
Some breakaway unions swore they would never return to the AFL-CIO, so there's talk of changing the name identified with organized labor for more than 50 years.
Leadership is tricky, too, with AFL-CIO president John Sweeney set to step down this year. The federation's secretary-treasurer, Richard Trumka, is a likely successor. But some unions, particularly the Teamsters, would oppose him.