Team USA authorities have warned American athletes that there will be "consequences" if they stage any political protests at the Tokyo 2020 Olympics.

The warning was issued after hammer thrower Gwen Berry and fencer Race Imboden were put on 12-months' probation after podium protests at the Pan-American Games in Peru. 

Berry raised her fist during the national anthem after she won gold in the hammer with a monster throw of 74.62m and Imboden took a knee standing on the top of the podium following victory in the team fencing event.

A letter was sent to both athletes from USOPC CEO Sarah Hirshland warning that protesting at future competitions would come at a bigger cost. This was in particular reference to the Tokyo 2020 Olympics for which both athletes are eligible.

In the letter Hirshland said: "We recognise that we must more clearly define for Team USA athletes what a breach of these rules will be in the future."

She added: "Working with the (athletes and national governing body councils), we are committed to more explicitly defining what the consequences will be for members of Team USA who protest at future Games."

Berry, 30, said she was protesting against social injustices in her country and that it is "too important not to say something," while Imboden said on twitter: "Racism, gun control, mistreatment of immigrants, and a president who spreads hate are at the top of a long list of issues that need to be addressed."

Hirshland reported that she respected the athletes' perspectives and would work with the International Olympic Committee "to engage on a global discussion on these matters".

"However, we cannot ignore the rules or the reasons they exist," she added.

The protests followed a number of demonstrations by American athletes started by NFL quarterback Colin Kaepernick in 2016 who took a knee during the national anthem to protest against racial injustice and police brutality in the USA. 

Megan Rapinoe has notably been the most recent to follow suit at this summer's FIFA Women's World Cup.