Triple jump and synchronised swimming are also sports identified as vulnerable under the changes approved by the IOC as part of a sweeping reform of the Olympics.

Australia's Jared Tallent has won silver at the last two Olympics in the 50km walk and with Nathan Deakes Australia has been on the dais in the 20-kilometre walk in two of the past three Olympics.

Australia also has a talented triple - and long - jumper in Henry Frayne, who jumped a personal best 17.23 metres two years ago as a 22-year-old before injury and who now is returning to fitness is a medal chance for Rio.  

The IOC approved a change to cap the total number of athletes at a summer games at 10,500 and 310 events instead of a 28-sport limit.

The changes will be not be introduced in time for the 2016 Olympics in Rio de Janeiro, but they appear likely to foreshadow the return of baseball, softball and squash for the 2020 Games in Tokyo given the popularity of baseball in particular in Japan.

Karate and surfing could also be introduced as Olympic sports as the IOC seeks to broaden the sports appeal and to attract younger sports fans. But for each event or sport added another existing sport must go.

"This is a major breakthrough," Canadian IOC member Dick Pound said. "We were at a dead-end situation with 28 sports."

Asked which events could make way for new sports, he replied: "Synchronised swimming and maybe triple jump."

Sebastian Coe, head of the British Olympic Association and IAAF vice-president, immediately sought to insulate triple jump from attack, saying: "Triple jump is a sacrosanct sport in track and field."

He also defended race-walking but acknowledged there was pressure on athletics saying: "There are roughly 10,500 athletes in an Olympics and we [athletics] take roughly 2200 - a fifth of all competitors and 47 different disciplines. Does that mean track and field needs to be vigilant about protecting its events then the answer is almost certainly 'yes it will'."

Other IOC members are understood to believe there are too many marginally different swimming events and there is need for reform there. Michael Phelps was able to win eight gold medals in one Games in 2008 due to the large number of similar swimming events.

Julio Maglione, president of swimming's international federation FINA, said: "I don't know what will happen, this is the truth, it's a difficult moment.

"I suppose that it's a problem we discuss in the future, we don't know what's going to happen with us, athletics, gymnastics."

In other rule changes - part of the greatest shake-up in the Olympics since 1999 - it was agreed that Games will be able to staged in more than one city or even in different countries in the future as the IOC sought to cut the increasingly prohibitive costs of hosting an Olympics.

The Age with agencies