By Drazen Jorgic

RIO DE JANEIRO (Reuters) - Kenya's Conseslus Kipruto stormed to an Olympic record breaking victory in the men's 3,000 meters steeplechase on Wednesday, ensuring the East African nation maintained its iron grip on an event it has monopolized since 1984.

The 21-year-old had long been touted as the heir to Kenya's steeplechase crown and made good on those predictions with a blistering final-lap sprint that carried him to gold in an Olympic best time of eight minutes 3.28 seconds.

A winner of two world championship silver medals, Kipruto was so far ahead of his rivals that he started celebrating and waving to the crowd when he entered the final straight.

"Even before the race I knew I would win," said Kipruto, who revealed he had suffered a calf injury days earlier.

The victory was the first in a major competition for Kipruto over Kenya's double Olympic champion Ezekiel Kemboi, who announced his retirement after initially finishing third but was subsequently disqualified for stepping out of his lane.

Prior to that decision, Kipruto thanked 34-year-old Kemboi for inspiring him over the years and promised to work hard to ensure Kenya maintained its record of winning consecutive Olympic gold medals in the steeplechase.

"I'm ready to take up the mantle," Kipruto said.

The African nation has now won every 3,000m steeplechase final it has competed in since 1968, having boycotted the 1976 and 1980 Olympics for political reasons.

Behind Kipruto, Evan Jager ran a fantastic race to claim a rare medal in the event for the United States -- their first since 1984 -- after overtaking Kemboi in the final 50 meters to take silver in an impressive 8:04.28.

"I just tried to stay as relaxed as I possibly could and hang on to Kemboi. He kinda looked back at me... on the back stretch, and I knew at that moment I might have him," Jager said.

"That was total joy."

Kemboi won his fourth steeplechase world championship title in a row last year.

"After 18 years I have done my best," said Kemboi, who won gold at the Athens and London Games.

Kemboi could not be reached for immediate comment on the decision to disqualify him. Kenyan officials lodged an appeal against the decision but organizers rejected it, upholding their initial decision to strip Kemboi of his medal.

France's Mahiedine Mekhissi-Benabbad was elevated to third place in the wake of Kemboi's sanction.

(Additional reporting by Scott Malone; Editing by John O'Brien)