UnitedHealth Group provided a lower-than-expected profit forecast for the year ahead on Monday, buffeting Wall Street's brighter expectations.

The nation's largest health insurance company said it expects earnings to be $5.25 to $5.50 per share in 2013, and revenue to come in at $123 billion to $124 billion, according to a regulatory filing a day before hosting the company's annual investors conference in New York City.

The forecast affirmed the Minnetonka-based company's previous outlook, but was below Bloomberg's average estimate of $5.58 in earnings per share.

Shares declined as much as 2 percent on Monday before closing at $53.53, down 39 cents. The UnitedHealth news may have dragged down share prices of other managed care companies, including Humana, Aetna, Cigna and WellPoint, whose shares took similar hits.

UnitedHealth Group CEO Stephen Hemsley foretold his qualms about the year ahead in October, after the company released its third-quarter earnings. Despite record customer growth, Hemsley said he expected lower gross margins at UnitedHealthcare because of greater competition for its Medicare Advantage plan for seniors, and reduced revenue from other government programs.

Hemsley also described a continued "weak business climate," contributing to slower jobs growth and a reluctance among businesses to offer insurance for their workers. The Affordable Care Act already limits the amount of profit insurance companies can make off of premiums they collect. In 2014, the law will add a tax on premiums to help pay for expanded coverage.

UnitedHealth has historically offered guidance on the low end, wrote BMO Capital's Dave Shove, and he wasn't giving a lot of weight to the announcement. The company easily topped its conservative forecasts in 2010 and 2011, he noted.

"We would not be surprised to see another landslide beat in 2013," Shove said. And with UnitedHealth projecting strong revenue along with declining costs, he said, "the coming year can continue to bring good tidings."

UnitedHealth's two distinct businesses and international growth make it one of the more diversified companies among the national insurers.

UnitedHealthcare, its insurance arm, provides health care benefits to more than 36 million people, making it the largest insurer for both Medicare and workplace-based coverage.

Its business services arm, Eden Prairie-based Optum, sells wellness programs, health information technology, accounting and management software, and has its own pharmacy benefits management company.

United has been investing in Optum, which is growing rapidly but still contributes a small slice of overall revenue. The strategy seeks to use Optum as a profitable counterbalance to the volatile and highly regulated insurance business.

Jackie Crosby • 612-673-7335