Alan Doherty from Letterkenny, Co Donegal said he was excited despite knowing the gruelling 10-hour surgery will cause him weeks of discomfort.

Alan was this afternoon due to undergo the pioneering surgery at the Sinai Hospital in Manhattan, New York.

The 17-year-old was born with an extremely rare maxillofacial disorder called octocephaly, which means he has no lower jaw or chin.

The bone for his jaw and mouth will be moulded from Alan's hip or fibia bone in a complicated procedure never before tried by doctors anywhere.

A second major operation will be carried out later this year with a series of follow-ups.

Alan and his parents Danny and Bernie flew from Dublin over a week ago to prepare for the surgery, as the campaign to raise the 250,000 euro (£169,000) needed to pay for a series of operations continued to gather pace in Ireland.

Alan who cannot breath unaided, eat normally or talk without the aid of his light writer keyboard wrote today: "I am enjoying New York since we came out. Everything is going well over here.

"Weather is nice. I am looking forward to Monday despite the pain I'll go through when the op's finished."

He added: "Everything went well yesterday. I got a small device into my mouth since yesterday's check-up.

"The device will be to widen my teeth apart from side to side until September or October."

The life-changing opportunity came about after Alan took part in the New York State 4D Games for the Physically Disabled and won 11 medals last year.

The USA team director Bill Broadwick - touched by Alan's request for a " perfect chin" when asked what he would like - set up an appointment with experts the next day.

Alan now looks set for a reunion with his former sporting rivals. He said: " May see my friends next week (after my operation) that I went to New York with last summer."

Paul McBride, who is helping co-ordinate the Friends of Alan Doherty Fund, said today: "He is in good spirits. He had his pre-op stuff on Friday and everything has gone well. They also held a press conference."

Donations from Northern Ireland can be sent by cheque to the Friends Of Alan Doherty fundraising account no: 15038040; sort code 937347.

The postal address is AIB Bank, Lower Main Street, Letterkenny, Co Donegal.