If the warming trend continues, the race held on Jan. 4, 1997, might have been the last.

The event takes place when the ice is at least 15 cm (5.9 inches) thick along the whole course, a condition that has been met 15 times in the past 100 years.

"Average temperatures are rising. In the last 10 years I have only been able to skate here one day. Otherwise there has been absolutely no ice," Henk Kroes, chairman of the race's organising committee, told NOS television as he gazed at an ice-free canal.

The "Elfstedentocht", considered one of ice skating's most gruelling challenges, attracts thousands of participants who try to cover almost 200 km (124 miles) on frozen canals through 11 towns in the province of Friesland, much of it in the dark.

The KNMI forecasts that the Netherlands will be able to hold only four races this 21st century, with the chances declining as winters get milder.

"The climate is getting warmer but the unpredictability is considerable so we could still get cold periods that would make the race possible," KNMI spokesman Harry Geurts said on Thursday.

Jan van der Hoorn, 83, winner of the 1947 race, was quoted as saying in the newspaper Volkskrant: "Something has definitely happened to winter: the daisies are still flowering in the grass and what if the North Pole were to melt?"