Xcel Energy and EnXco, the developer of a North Dakota wind farm that poses potential risk to two species of endangered birds, have sued each other over the utility's decision to drop out of the project.

The two companies filed suits Wednesday in U.S. District Court in Minnesota, asking for a ruling on whether Xcel has the legal right to withdraw from its contract to acquire the proposed $400 million Merricourt project.

Xcel, the Minneapolis-based electric and gas utility, withdrew from the 100-turbine project five weeks ago, citing delay and higher cost to protect the birds. EnXco alleged in its lawsuit that Xcel wanted out because electrical demand is down.

Just last week, both sides took steps that suggested the disagreement might be over. EnXco refunded Xcel's $100 million down payment, and Xcel said it will look for other wind projects, possibly partnering with EnXco, the American subsidiary of EDF Energies Nouvelles, at another location.