OSLO (Reuters) - If you think you might win the Nobel Peace Prize on Friday, drop everything if a man phones saying he's a journalist from an obscure Norwegian newspaper.

Geir Lundestad, director of the Norwegian Nobel Institute, tries to phone winners before the prize is announced in Oslo but sometimes has to disguise who he is to avoid leaking the closely guarded secret to the media.

"I try to call the winner, but some years it's not possible," he told Reuters. This year's prize will be announced on Friday at 0900 GMT, and Lundestad tries to call an hour or so in advance.

Last year, when the prize went to former U.S. Vice President Al Gore and the U.N. Climate Panel for their roles in fighting global warming, Lundestad phoned the office of Rajendra Pachauri, the head of the Climate Panel, in New Delhi.

He told the secretary who answered the phone that he was a reporter from a small provincial Norwegian newspaper and then asked if there were many journalists around Pachauri in his office.

When told "yes", he said he hung up, fearing he might give the secret away.

"The media were swarming here so he called off," Pachauri told Reuters. Winners in the United States, like Gore, sometimes do not get a call because it is night-time.

Still, Pachauri said he got a call from Oslo from another contact before the prize announcement.

"I still didn't believe it until 15 minutes before the announcement when I got a message that the Norwegian ambassador was on the way. Then I knew that something had happened," he said.

The five-member committee is often seeking to clamp down on leaks. It says it tells the Foreign Ministry of the winner's identity shortly before the announcement.

Lundestad said he did not want a repeat of 2004, when Kenya's Wangari Maathai, who won for a drive to plant trees across Africa, told Reuters 23 minutes before the prize announcement that she had been told she had won.