Northeast Utilities and National Grid had agreed to purchase more than 75 percent of the power produced by Cape Wind’s planned 130-turbine wind farm in Nantucket Sound. Today, the utilities attributed their decision to terminate the contract to Cape Wind’s failure to meet a Dec. 31 financing deadline for the $2.5 billion project.

“National Grid is disappointed that Cape Wind has been unable to meet its commitments under the contract, resulting in [the] termination of the power purchase agreement,” National Grid spokesman Jake Navarro said in a statement.

Northeast Utilities spokesman Michael Durand wrote in an email that, under the terms of the contract, Cape Wind could have posted financial security in order to extend the deadline for financing but decided not to.

“Therefore the contract is now terminated,” he wrote.

Cape Wind has previously characterized its power purchase agreements as key to securing financing, and the utilities’ decision raises questions about whether the developer will be able to close financing without the contractors.

But Cape Wind spokesman Mark Rodgers said the developer does not “regard the decision to terminate the contract as valid,” citing a contract provision that would allow delays in reaching project milestones caused by “unusual, unexpected and significant events.”

Those events should include the “unprecedented and relentless litigation the Alliance to Protect Nantucket Sound” has filed to block the project, Cape Wind President Jim Gordon wrote in a letter to the utilities Dec. 31 urging them not to terminate their contracts.

The alliance, which opposes the project for economic and aesthetic reasons, has filed more than 20 administrative and judicial challenges to Cape Wind.

“This exceptional level of litigation against Cape Wind for the purpose of delay is extraordinary, unusual, unexpected and significant,” Gordon wrote. “It has been completely beyond Cape Wind’s control and could not have been prevented or avoided.”

Gordon said he expected the project to overcome the latest challenge and secure financing in 2015.

Alliance President and CEO Audra Parker heralded the utilities’ decision, saying it “speaks to the poor economics of the project.”

Northeast Utilities had agreed to purchase 27.5 percent of Cape Wind’s production, and National Grid had agreed to purchase 50 percent. The average residential electricity customer would have paid an extra $1.50 per month under the contract.

“This is very bad for Cape Wind but great news for ratepayers across Massachusetts,” Parker said.

Outgoing Massachusetts Gov. Deval Patrick (D) has championed the Cape Wind project since taking office in 2007. His administration has even funded the construction of a $100 million new port facility in New Bedford, Mass., to cater to the needs of the offshore wind industry. In September, Cape Wind signed a lease to use the facility beginning in 2015.

Patrick spokeswoman Jesse Mermell said today that the news about Cape Wind has not put a damper on the governor’s enthusiasm for the industry.

“The future of offshore wind in the commonwealth remains bright,” she said.