LandSource Communities Development LLC, the joint venture that owns Santa Clarita’s Newhall Land & Farming Co., said it filed for Chapter 11 bankruptcy late Sunday.

The company, which built the city of Valencia, is developer of the proposed 21,000-home Newhall Ranch project west of the Golden State (5) Freeway in the Santa Clarita Valley. The 15,000-acre project has been hard hit by the credit crisis and end of the region’s housing boom.

LandSource said it had received commitments for debtor-in-possession financing from a group of lenders led by Barclay’s Bank, including a $135 million revolving line of credit.

Newhall Land is the primary investment of LandSource, which is based in Aliso Viejo. The California Public Employees’ Retirement System, the nation’s largest public pension fund, is a major investor in the venture.

“We regret that LandSource was forced to file for bankruptcy protection and hope that the parties will be able to reach an equitable solution,” said MacFarlane Partners in a statement on Monday. MacFarlane, a San Francisco-based real-estate adviser, had helped arrange the land deal for to Calpers and manages its interests in the project via MW Housing Partners. “We agree with LandSource that, in the long term, this investment will be seen as a good one.”

Citing unnamed lenders, Standard & Poor in April predicted the company would soon seek protection from creditors. The debt ratings company said the company’s cash had declined to about $25 million from about $115 million in early February. A LandSource spokeswoman confirmed soon after that the company had received an official notice of default on a $1 billion loan.