Iowa Senator Tom Harkin is leading congressional negotiations on a bill that’s backed by unions.

"We’re continuing our negotiations and talks about how we change the environment so that it’s more condusive for workers to freely join or not join a labor union," Harkin says. "We’re making progress."

Business interests have blasted the bill and there have been published reports suggesting a key component of the legislation has been axed. That provision would have allowed workers to fill out registration cards and form a union that way, without taking a vote.

"These are very delicate negotiations. I was very proud of the fact that nothing had leaked out about on these before, but then someone decided to talk to the press last week. I don’t know who it was," Harkin says. "But I’m not going to confirm, I’m not going to deny anything that came out."

All 60 Democrats in the U.S. Senate would have to unite and support the bill to avoid a likely Republican "filibuster" that would prevent a vote on the legislation. There have been reports that some moderate Democrats are balking at the legislation.