The open category will give transgender athletes a chance to race on the elite stage after they were effectively banned from female events by the governing body at last year's Extraordinary Congress.

A rule was implemented that anyone who has undergone male puberty would not be allowed in a women's race.

The open category will feature races in the 50 and 100-metre distances across all strokes, while the possibility of introducing additional events remains.

Participants in the open category will compete over two days in timed finals.

To be eligible, swimmers need an affiliation with a national federation and will be given the flexibility to participate individually, for their club, team or as national federation members.

"When World Aquatics instituted its policy on eligibility for the men's and women's competition categories, we committed to exploring the creation of an open category," said World Aquatics President Husain Al-Musallam.

"True to our word, a team of experts has diligently worked to make this a reality.

"I would like to thank all those who have helped World Aquatics to deliver this opportunity." 

Berlin is the first of three stops over three consecutive weeks of the Swimming World Cup, with events also scheduled in Athens and Budapest.

Deutscher Schwimm-Verband vice-president Kai Morgenroth has welcomed the move to allow transgender athletes to compete.

"Berlin is thrilled to champion this groundbreaking initiative with the full endorsement of the German Swimming Federation," said Morgenroth.

"We're proud to host an event where swimmers can compete without barriers. 

"Berlin is Germany's hub for diversity and inclusion and therefore the perfect location for such a progressive project."

Al-Musallam pushed for the creation of an open category as he wanted to give everyone the opportunity to compete at an elite level.

Despite this, some transgender athletes have expressed concerns about the concept of an open category. 

"[World Aquatics'] choice to force trans women into an 'open' category with cisgender men is an unethical non-starter," trans cyclist and twice International Cycling Union Masters world champion Veronica Ivy said.

"It is the very definition of 'separate but equal' and an extreme indignity to the women affected.

"Trans women are legally, socially, and medically women; we are legally, socially, and medically female.

"We ought to race with women and international sports federations need to cease placing limits on who is 'woman' or 'female' enough."