Kansas City, Mo. ? Aquila Inc. will exit the wholesale energy trading business by the end of September, becoming the latest energy company to do so amid weak prices and tougher scrutiny from regulators and credit rating agencies.

In June, the company announced plans to shift its focus from the unregulated wholesale energy services and seek a partner or buyer for that business as it looks to firm its balance sheet. Instead, Aquila has eliminated all market-making activity.

“While we had explored the idea of securing a partner, we believe it is in the best interest of our shareholders to completely exit the wholesale energy marketing and trading business,” said Robert K. Green, president and CEO.

Instead of trading energy, on which the company once staked its future, Aquila once again will depend almost entirely on income from regulated utilities and unregulated power generation, which have more stable cash flow than trading.

After the late-September shutdown of the energy trading business, the company will only market energy from assets the company owns or controls, Aquila said.

Shares of Kansas City, Mo.-based Aquila closed Tuesday at $5.74 on the New York Stock Exchange, unchanged from a day earlier.

Like many energy companies, Aquila soured on the deregulated wholesale market in recent months as the cost of capital soared and earnings proved elusive amid weak prices.

Several companies, including Houston-based Dynegy Inc. and Tulsa, Okla.-based Williams Cos., have had to cut back on trading, put assets up for sale and renegotiate with lenders. Those companies and numerous others also are under investigation by the Federal Energy Regulatory Commission and the Securities and Exchange Commission for possible abuses in accounting and trading.

Aquila’s credit rating currently is one notch above junk status and is under review by Moody’s Investors Service and Standard & Poor’s. A credit rating downgrade would increase financing costs and trigger covenants that would require repayment of debt if a rating sank to junk.

To conserve cash, the company has sharply cut its dividend and said it may eliminate it altogether.

Since May, Aquila has cut about 550 jobs related to the wholesale energy business. It expects to cut 500 more jobs because of the decision.