Duke Energy and Progress Energy art working against the clock to get their merger deal done by July 8, after which it has the potential to unravel, at least legally.

After that date, either company could walk away or try to change the terms in their bid to become the largest U.S. utility, with 7.1 million customers.

In  hopes of goosing the process toward completion, the companies asked for action by June 8 on a plan they filed with the Federal Energy Regulatory Commission on Monday. That mitigation plan says they would build transmission projects to bring wholesale power into North Carolina to encourage competition, an issue FERC had with their original plan.

If they get federal action when they hope they will, they then have a month to persuade state regulators that they should bless the merger. The state has not been a cheerleader for the proposal so far.