Washington ? Union leaders are talking about reuniting under a single, more powerful federation, nearly four years after a nasty breakup split organized labor.

Leaders from 12 of the largest unions, along with rival federations AFL-CIO and Change to Win, have held three meetings since January aimed at setting aside differences and taking advantage of the most favorable political climate for unions in 15 years.

“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.

The political landscape has changed now that Democrats control the White House and Congress. Union officials see a chance to accomplish goals such as passing legislation that would make it easier for workers to organize unions.