LONDON (Reuters) - British enthusiasts have launched a bid for the ancient sport of jousting, in which riders in steel armor charge and try to knock each other off their horses with a 12-foot (3.7 m) pole, to be made an Olympic sport.

Long a feature of themed medieval fairs in the grounds of ancient castles, jousting deserves to be recognized as a "western martial art" and added to the roster of Olympic events, said professional jouster Dominic Sewell.

"You can see jousts from Russia to Australia to western California," Sewell, suited up in chain mail, told Sky TV on Thursday.

"It's becoming a truly international sport and that's why we are calling for it to be recognized on an Olympic level."

Sewell is backed by English Heritage, a charity that curates 400 historic buildings, monuments and sites, and has launched an online petition to promote jousting ahead of the Rio Olympics.

Medieval knights turned to jousting to showcase their strength, skill and horsemanship, with the first tournament held in 1066 and similar spectacles patronized by King Henry VIII and Queen Elizabeth I.

Encounters often ended in injury or death - including of French King Henry II in 1559 - but the hollow lances used nowadays are designed to shatter on impact, reducing the risks.

Sewell said jousting combines the demands of the Modern Pentathlon with the horsemanship of other equestrian events already on the Olympic roster. He described his armor as "personal protection equipment - it just happens to be made of steel."

It would take years, however, for jousting to be considered for inclusion in the summer games.

First it would have to be recognized as an Olympic sport and then scrutinized for a period of at least seven years. A recognized international jousting federation would need to be established and world championships held.

While no new sports have been added for Rio, baseball and softball, karate, sport climbing, skateboarding and surfing have been recommended for inclusion at the 2020 Tokyo Olympics.

(Reporting by Douglas Busvine; editing by Stephen Addison)