ST. LOUIS -- Ameren Corp. expects to ask Missouri regulators by the middle of this year for another electric rate increase, the St. Louis-based utility said Thursday.

The expected rate increase request was mentioned in a news release in which the company refined its 2007 earnings-per-share guidance. Ameren spokesman Tim Fox said he was not sure of the specific amount that would be sought.

In May, the Missouri Public Service Commission granted a $43 million rate increase to Ameren despite the objections of state public counsel Lewis Mills Jr. and Attorney General Jay Nixon. Both contended Ameren not only didn't deserve a rate increase but should instead be forced to lower electricity rates.

Calls to Mills, who represents consumer interests, and Nixon, who represents the state, were not returned.

Ameren serves about 2.4 million electric customers in Missouri and Illinois, along with about 1 million natural gas customers in the two states. The company is also seeking $247 million in combined electric and natural gas rate increases in Illinois.

Chairman and chief executive officer Gary Rainwater said Ameren doesn't expect the new rates to be effective until late 2008 in Illinois and early 2009 in Missouri. He said the increases are necessary to offset rising costs and investment needs.

"Current rate levels are not sufficient to recover our existing costs," Rainwater said in the release. The company plans to seek the Missouri rate increase in the second quarter.

Ameren executives were meeting Thursday with analysts and investors in New York.

The company previously projected full-year earnings of $2.80 to $3.05. A revised outlook narrows the range to $2.90 to $3 per share. Ameren also said it now expects compound annual earnings growth of 4 percent to 6 percent through 2010.

Ameren expects to invest $5.7 billion to $6.7 billion in its business through 2012, including investments aimed at making the utility more environmentally friendly, Rainwater said.

"Our customers and communities count on reliable energy and want clean air, and these investments in our utility infrastructure are targeted to meet their needs," he said.

Last week, a judge approved a $180 million settlement over the December 2005 collapse of Ameren's Taum Sauk reservoir in southeast Missouri. The incident spilled 1 billion gallons of water, injuring a family that lived nearby and badly damaging a popular state park.

The guidance does not reflect the Taum Sauk settlement because some of the $180 million is in-kind improvements that have not yet taken place, Fox said. Insurance is expected to cover substantially all settlement costs and the costs of rebuilding the upper reservoir.