The International Olympic Committee has decided to change the way new sports are included in future Games.
Baseball and softball have been dropped for 2012
Delegates agreed to reduce the number of sports for the 2020 Games to 25 during a two-day meeting in Kuwait - with three potentially voted in.
The IOC has also decided to alter the voting procedure for new sports.
Just a majority of votes will be needed to bring in a sport compared to the current two thirds and the new system will come into affect next year.
The IOC said the changes would make the process of introducing new sports more exciting.
"This will be more interesting for sports wanting to come in," said IOC Olympic Games executive director Gilbert Felli.
"It will make the process less conservative and more flexible."
The Beijing Games in 2008 will be the last to feature a core of 28 sports as baseball and softball were removed from the London Games in 2012.
For the 2016 Games, the IOC will have a core of 26 with the possibility of introducing two more.
The IOC had already decided that Games should have a maximum of 28 sports and a minimum of 25.