* H1 profit drops 92 pct to 10 mln euros vs fcast 8 mln loss
* Books 28 million euro one-off tax on 2009 earnings
* H1 net interest income up 12 pct to 591 mln euros
* BofA Merrill Lynch, UBS, Goldman to advise on buyouts
* Piraeus Bank shares closed up 3.75 pct vs index up 1.7 pct (Adds advisers on offer to buy state bank stakes, details)
By George Georgiopoulos
ATHENS, Aug 26 (Reuters) - Piraeus Bank, Greece's fourth-largest lender, on Thursday reported a sharp drop in first-half profit, hurt by a one-off retroactive tax on 2009 earnings, weak loan growth and higher provisions.
The bank said net earnings fell 92 percent to 10 million euros ($12.7 million), beating market expectations. Analysts on average were forecasting a loss of 8.0 million euros.
"Results were a bit better than we expected as a result of stronger commission and net interest income," said analyst Nikos Lianeris at Alpha Finance. The group booked a 28 million euro windfall tax, the government imposed to shore up public finances in the second quarter.
"In the second quarter Piraeus managed the volatility of the economic environment and succeeded in improving organic profitability," Chief Executive and Chairman Michael Sallas said.
"According to current indications, the group's performance is expected to be resilient."
A deepening recession in Greece weighed on loan demand and asset quality, leading to higher loan-loss provisions in the first half which rose 30 percent to 268 million euros.
Access to wholesale funding has also remained closed due to the debt crisis, forcing Greek lenders to turn to the European Central Bank.
Piraeus Bank said net interest income rose 12 percent year-on-year to 591 million euros. Its net interest margin improved to 2.7 percent from 2.5 percent.
"Net interest income should be resilient unless something drastic happens to the deposit market," Deputy CEO Alex Manos told analysts in a conference call.
The group, which has offered to buy government stakes in ATEbank and Hellenic Postbank for 701 million euros in cash, said it hired BofA Merrill Lynch, Goldman Sachs and UBS as advisers on its offer.
Piraeus -- also present in Romania, Bulgaria, Serbia, Albania, Cyprus, Egypt, Ukraine and the United States -- said its deposits were down 7 percent in the first half, while its loans-to-deposits ratio rose to 111 percent from 107 percent.
Piraeus shares have fallen 50 percent since the start of the year, underperforming the Greek equity market's 31 percent drop. They closed up 3.75 percent at 4.15 euros before the results were announced. The ASE main index closed up 1.69 percent.
They trade at about 9.8 times estimated 2010 earnings, compared with a P/E ratio of about 12.5 for European peers, according to Reuters Estimates. (Editing by Sharon Lindores)