LOS ANGELES (AP) — Grubb & Ellis Co. said Tuesday it has sought bankruptcy protection as part of a deal to sell most of its assets to the parent of rival commercial real estate services company Newmark Knight Frank.

The proposed sale to BGC Partners Inc. comes as Grubb & Ellis struggles with mounting debt after posting operating losses for several years following the real estate downturn. The deal will require court approval as part of Grubb & Ellis’ Chapter 11 bankruptcy process.

“We are pleased to have found such a strong partner who can provide our company with financial stability and deeply enhanced opportunities,” Thomas D’Arcy, Grubb & Ellis’ president and chief executive, said in a statement.

The Santa Ana-based company filed for bankruptcy protection Monday in the Southern District of New York.

In the filing, it listed $150 million in assets and $167 million in debt as of the end of last year. The company also said it had more than 5,000 creditors.

In documents submitted to the bankruptcy court, Grubb & Ellis Chief Financial Officer Michael Rispoli outlined the circumstances that led the company to seek shelter from creditors.

He noted that Grubb & Ellis has sustained losses largely related to the meltdown of the financial markets around 2008, the slower-than-projected recovery of the real estate market and its 2007 merger with NNN Realty Advisors Inc.

“The combined effect of these adverse economic conditions and liabilities and losses associated with disposed businesses severely strained Grubb & Ellis’ liquidity and hampered its ability to continue as a going concern,” Rispoli said.

Grubb & Ellis attempted to restructure its operations a year ago by launching a process aimed at divesting itself of non-core businesses, including NNN Realty Advisors and its Alesco Global Advisors mutual fund operation.

It also sought out new financing sources for its remaining operations, while putting out feelers to sell some or all of its operations. But the company failed to reach a deal that could be done outside of bankruptcy protection.

Grubb & Ellis is asking the court to approve an expedited sale process and hearing, noting that concerns over its financial stability prompted brokers representing nearly 30 percent of the company’s 2011 brokerage revenue to leave the company — a trend the company says is likely to continue.

BGC, which is based in New York, has agreed to provide up to $4.8 million in financing to keep Grubb & Ellis operating while in bankruptcy.

Shares of BGC were unchanged in regular trading on Tuesday at $6.74.