Australia's Primary Health Care offered to buy Symbion Health for A$2.7 billion (US$2.5 billion) in cash, rivaling an offer of cash and shares by Healthscope and private equity firms.
Primary said it would offer A$4.10 for every Symbion share, a 2.5 percent premium on Symbion's last trade.
The long-awaited offer is the latest in a year-long battle for pathology and diagnostic imaging assets, coveted as Australians age and increasingly rely on private health care.
Symbion is already the subject of a revised A$2.8 billion tie-up offer from Healthscope, which Primary, with a 20 percent stake in Symbion, is opposing.
Primary plans to raise A$170 million (US$139 million) through a placement of 15.5 million shares at a floor price of A$11.00 each to help fund its bid, a source familiar with the matter told Reuters.
Primary shares last traded at A$12.29 ahead of a trading halt.
The rival bid from Healthscope, Archer Capital and Ironbridge Capital values Symbion between A$3.54 and A$4.45 a share, according to Ernst & Young.
Under their plan, Healthscope would buy Symbion's pathology, diagnostic imaging and medical centers business for shares, and the two private equity firms would buy Symbion's consumer and pharmacy businesses for around A$1.15 billion in cash.
Deutsche Bank, Credit Suisse and ABN AMRO are the book runners for Primary Health's share placement, the source, who declined to be named, said.