COPENHAGEN, Denmark (Reuters) - More than 100 Father Christmases hold their annual get-together in Copenhagen next week -- but Finland's one and only, real Santa Claus says he is too busy welcoming visitors to leave his Arctic home.

"I have so many guests here every day, people from all over the world. I cannot let them down," Santa told Reuters by telephone on Friday from his home in Lapland, northern Finland.

The Finnish Santa, who says children round the world know him as the real Father Christmas, said he received up to 4,000 visitors a day, adding up to several hundred thousand a year.

Santa, who is nearly 400 years old, said the 35th Santa Claus World Congress to be held in Copenhagen from July 20-23 was a gathering of his semi-official assistants -- a view that might irritate some of his rivals.

Some claim that Santa Claus lives in Greenland, others believe he comes from Turkey, but Finland's Santa stated unequivocally that he was the one and only real Father Christmas.

The special Father Christmas post office in Finland received over 800,000 cards or letters from children in nearly 200 countries last year, and one million are expected this year, he said.

If this, and his many visitors, do not prove that he is the real Santa, doubters should try to visit the other Santas. "You will find nothing," he said. "There are a lot of fakes around, just like in the CD (compact disc) market."

"I am here all the time, apart from Christmas when I visit children all over the world."

Santa said he did not mind not having been invited to the World Congress for the past two or three years. He attended it once in its early years, but found that it did not suit his schedule.

"Everyone wants to see the real Santa Claus here," he said.

The Danish Santa Claus Association said over 100 Santas from about 10 countries will meet in Copenhagen "for a serious congress." Agenda items include a debate on whether Christmas Eve should be moved to January 6 from December 24.

"A dispensation might be given to the countries that don't want to celebrate Christmas Eve on December 24," it said in a statement.

One key topic will be a demand by the Santas' wives to have their own trade union. "They want to be independent, have the right to vote at the congress and they want to be called 'Female Santa Clauses'," the association said.

The four-day event will also feature a Santa Claus parade through the city center, open-air shows, dances and games, the organizers said.