Domingo stills performs in operas around the world

"The day is close that I quit singing," said the 64-year-old tenor.

"I really don't know how to do it - a tour or a concert or if I just say, that's it, that's the last night."

The singer, one of the renowned Three Tenors, also said he did not want to make "a comeback" just a couple of years after retiring.

One of the main reasons for considering retirement now was the increasing age gap between himself and fellow performers.

Last ambition

When his career began, he was singing opposite women old enough to be his grandmother, he said - but female leads are now young enough to be his granddaughter.

One last ambition is to sing the baritone role in Verdi's opera Simone Boccanegra, he said.

One of Domingo's Three Tenor colleagues, Luciano Pavarotti, is currently giving a farewell world tour.

He originally said would visit 40 cities in 2005 but so far has given no indication of when his final performance will be.