Sisniega was approved as part of the new structure of FMF earlier this month.

The Mexican leaves Panam Sports four months before the Santiago 2023 Pan American Games starts.

The former modern pentathlete and Sports Minister of Mexico was appointed as secretary general by Panam Sports President Neven Ilic in 2017.

Sisniega replaced compatriot Jimena Saldan and held onto his position when Ilic was re-elected as President in 2020.

The 65-year-old said it was a "difficult choice" to make when FMF came calling but thanked Ilic for "understanding" his decision.

"I was very happy at Panam Sports," Sisniega told insidethegames.

"It was a difficult choice when I got the offer to join the Mexican Football Federation.

"It has been six years working together with Neven.

"We have been able to move Panam Sports forward and this is a new challenge for me.

"Neven was very understanding and wished me the best.

"I will look forward to maintaining my friendships at Panam Sports.

"It was a sentimental decision but one that was needed at the moment.

"I will attend the Games in Santiago.

"I wish them well and I will continue to keep an eye on how things are going.

He said that both positions were full-time, and he had no choice but to leave one.

Sisniega however will continue to be chairman of the International Modern Pentathlon Union's (UIPM) Innovation Commission.

The UIPM Innovation Commission made the controversial recommendation to axe riding from the sport after Paris 2024.

The decision by UIPM Executive Board in October 2021 to cut riding played a crucial role as modern pentathlon was left out of the initial sports programme for Los Angeles 2028.

Obstacle racing was approved as the sport's new fifth discipline at last year's virtual UIPM Congress.

"Mexican football is in a difficult moment right now and it is a great opportunity to work on restructuring the most popular sport in Mexico," he said.

"I will continue to be chairman of the Innovation Commission.

"Based on the decision of IOC [International Olympic Committee], in October we will meet to discuss the new challenges.

"We are all waiting for the decision.

"It is an exciting time for pentathlon, and we are eagerly waiting for this new direction for the sport.

"Both positions are really full-time positions.

"It is not possible for me to work with Panam and FMF together."

Modern pentathlon's Olympic future will be one of the main topics discussed at the IOC Session Mumbai in October, which is scheduled for October 12 and 13.

Replacing riding with obstacle racing has not gone down well with many athletes, including Olympic and world champions.

Critics including pressure group Pentathlon United, whose members include the Tokyo 2020 champion, Britain's Joe Choong, have opposed the decision to replace riding.

Sisniega is hoping that the IOC realises the "exciting new opportunity" with obstacle racing.

"What I am seeing is a group of athletes from a small number of nations who have the privilege of having horses and facilities to train and compete are the ones wanting to keep riding," Sisniega said.

"I think it’s unfortunate that they are still thinking having horses is the solution.

"I was part of the rigorous process to find a new discipline and the best solution was found with obstacle.

"It is new and tests various skills of the athletes and is an exciting new opportunity for the sport to grow.

"I think it is a great opportunity and hopefully the IOC will see it that way as well and takes advantage of it."