The IAAF has expressed concern at a proposed reduction in athlete numbers for the 2020 Olympic Games in Tokyo, brought about by an event shake-up.

The IOC on Friday revealed a list of approved events for the Games, which placed a focus on gender balance and a more "youthful" and "urban" approach.

Among the plans is a new 4x400m mixed relay for the athletics schedule, while 105 fewer athletes would be entered under the proposals.

The IAAF's concerns focus mainly on a crowding of the schedule for the athletes who are in attendance and the impact of the changes on the smaller competing nations.

A statement read: "We should not expect the athletes entered to compete in the men's and women's 4x400m relays, from which the participants for the mixed relay will be naturally drawn, to compete in a third round of heats and finals for the mixed relay without allocating the appropriate space and time in the programme or enabling teams to bring additional athletes. 

"The IAAF is naturally disappointed by the reduction in the athlete quota for the athletics competitions.

"Whilst we understand the need to be firm on numbers and applaud the IOC's stance on gender equality in all sports, reducing the quota will inevitably have an impact on our joint goals of universality. 

"There are 10 nations and most of the refugee team who competed only in athletics at the Rio 2016 Olympic Games.  Just one of those nations met the qualification standards, the athletes from all the others (over 20) were awarded wild cards.

"To implement the reduction in the overall number of athletes, the qualification system and entry standards for athletics at the Olympic Games would have to be reassessed to bring them into line with the higher level of the IAAF World Championships. At those championships there is a quota of one non-qualified athlete per each nation who are allowed to enter EITHER one male OR one female athlete irrespective of whether they have qualified."

President Sebastian Coe added: "Athletics is the number one sport at the Olympic Games, so we want to work with the IOC to drive effective and meaningful change.

"We have agreed to look at the reduction in quota challenge to see what impact it will have on athletes and nations competing in athletics given that 10 countries compete only in our sport. 

"We will also work with the IOC on how best to introduce a mixed relay event in Tokyo following the huge success the mixed relay has enjoyed in IAAF World Relays and Nitro Athletics this year.  

"All proposals will go to the IAAF council to review and approve at its council meeting ahead of the IAAF World Championships in London this August."