The Four Seasons group is to convert the top floor of its Ballsbridge hotel into some of the most expensive apartments in the State.

The luxurious private residences, which will be the first in a Four Seasons hotel in Europe, are likely to be developed early next year and should be ready towards the end of 2006.

The hotel's general manager, Mr John Brennan, said the apartments would be priced "towards the upper end of the scale". The group already runs similar projects in some of its hotels in the US and a corresponding apartment in Miami or San Francisco can cost $6 million (€4.5 million).

It is expected there will be between 15 and 20 properties for sale. Although this will reduce the number of rooms in the hotel from 259 to 200, buyers will be able to lease the apartments back to the hotel when not in residence. The development will represent a significant cash injection for the hotel's owners, the Nollaig Partnership.

Mr Brennan said the Republic was chosen as the first location in Europe for this sort of development because of the strong connections between Ireland and the US. "We believe this is a concept that is right for Ireland at the moment, both for Irish citizens and people with Irish connections," he said. "It reflects the emergence of Dublin as an increasingly important commercial centre and travel destination in Europe.

"More and more Americans are buying two homes in, say, San Francisco and New York, so why not in San Francisco and Dublin?

"We expect demand for the homes to be strong. Buyers will have full access to all the hotel's services, including valet service, a 24-hour concierge and peace of mind regarding security that they may not have in an apartment building."

Mr Brennan said the loss of 60 rooms would not lead to a significant drop in revenue, and that the lease-back initiative would provide the hotel with individualised suites for its wealthier guests.

"If owners don't plan to spend all year in residence, they can rent the room back to us while they're not there," he said. "These suites will be unique as they will feature both the original hotel fittings and whatever additions the owner has made."

Members of the Nollaig group include property developers Mr Mark Kavanagh and Mr David Arnold, former attorney general Mr Dermot Gleeson and Mr Donal Geaney, chairman of the National Pension Reserve Fund.