Updated from 11:24 a.m. EDTHilton Hotels ( HLT) and the international business it spun off four decades ago could be headed for a warm reunion. But Hilton Hotels' investors -- cognizant of a potential deal's near-term impact on earnings and Hilton's balance sheet -- are giving the news a decidedly cold reception, and shares slumped as much as 6% in New York Friday. Hilton Hotels of Beverly Hills, Calif., is talking to London-based Hilton Group PLC about buying the latter's hotel unit, which owns and manages the Hilton brand outside the U.S., the companies confirmed. Investors in the U.S. company have plenty to be concerned about. Media reports citing anonymous sources put the price tag at about 3.6 billion pounds, or $6.3 billion. Given that Hilton Hotels cash hoard recently totaled $691 million, it probably would have to take on significant debt to finance such a purchase. That would mark a change from recent years, when the company cleaned up its balance sheet by selling nonstrategic hotels and paying down debt. The potential for more debt is likely the reason Standard & Poor's put Hilton Hotels' credit rating on negative watch Friday. Riding the strong lodging recovery, Hilton Hotels has also been returning extra cash to investors by aggressively repurchasing its own stock. In the second quarter, for instance, it snapped up 5.1 million shares. "Given our sense that many investors were in the stock 'for the excess free cash flow going to share repurchase' theme, we think we could see some rotation out of Hilton Hotels," wrote Bear Stearns analyst Joseph Greff, in a research note Friday. "We think Hilton Hotels needs to address why it thinks now is the right time to make an acquisition -- is it because it sees its domestic growth slowing in the near term?"