Gennady Golovkin aims to set up a world middleweight title unification fight with Billy Joe Saunders should his rematch with Saul 'Canelo' Alvarez be cancelled.

WBA, WBC, IBF and IBO title-holder Golovkin is scheduled to face Canelo at T-Mobile Arena in Las Vegas on May 5, but the bout has dark cloud hovering above it - after the Mexican superstar failed a voluntary drugs test.

Golovkin recently erupted during a media interview and took aim at Canelo, as he told reporters on Tuesday that he felt Mexican boxer was a longtime user of performance enhancing drugs and claimed to have photos that allegedly showed physical evidence of injections on Canelo's body - and GGG claims to have videos of Canelo taking unknown pills.

The Nevada Athletic Commission (NASC) is investigating, but Golovkin has moved to identify an alternative opponent, with Saunders currently holding the WBO belt that would complete the Kazakhstani's set.

"If the fight can't happen, the next step for me is Saunders," Golovkin was quoted as saying by the Daily Mail. "It is my dream to get all the world championship belts."

He added: "I still hope the fight [with Canelo] happens. It is the biggest fight in boxing right now and I would like to be on that level once again. But it is for the [NASC] to decide if he was positive or negative."

Canelo vehemently denied any wrongdoing following news of his failed test, insisting: "I am an athlete who respects the sport and this surprises me and bothers me because it had never happened to me.

"I will submit to all the tests that require me to clarify this embarrassing situation and I trust that at the end the truth will prevail."

The first fight between Golovkin and Canelo, in September 2017, ended in a controversial draw.

Saunders is set to defend his WBO title against Martin Murray in London on June 23.