CHICAGO (Reuters) - Health Management Associates Inc. <HMA.N>, one of the biggest U.S. hospital chains, on Friday warned quarterly and annual results will fall short of Wall Street estimates, blaming weak patient admissions and the rising burden of unpaid medical bills.

Hospitals executives and analysts have said they do not see a short-term solution to weak admissions and unpaid bills, problems that plague the industry. They had been hoping for some stabilization, but it may not happen this quarter.

It "bolsters the probability of seeing a challenging June quarter for the hospital group," Raymond James analyst John Ransom said.

"There are no signs of improvement in the second quarter," said Rob Mains, an analyst at Ryan Beck.

HMA, which runs 62 hospitals in non-urban areas primarily in the U.S. Southeast, said it expects second-quarter earnings of 31 cents to 34 cents per share, below analysts' average forecast of 36 cents.

For 2006, it expects to earn $1.30 to $1.34 per share, compared with analysts' average estimate of $1.43.

Hospitals are struggling with treating the increasing rolls of the uninsured, about 46 million people in the United States. At the same time, patients with insurance are putting off treatment because of increasing costs to consumers. That is weighing on admissions, especially for more lucrative elective procedures.

The company also announced a $250 million stock buyback program.

Shares fell $1.06 cents, or 5 percent, to $19.57 on the New York Stock Exchange in mid-morning trade. HCA Inc.<HCA.N> , the biggest U.S. hospital chain, fell 1 percent, while Tenet Healthcare Corp. <THC.N>, the second-biggest chain, fell about 2 percent, both on the NYSE.

_____________________________________________

Copyright 2006 Reuters News Service. All rights reserved.