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 poised to face Alvarez in Las Vegas on May 5, but the bout has been placed in doubt after the Mexican failed a voluntary drugs test.

Alvarez tested positive for trace levels of the banned drug clenbuterol, with his promoters blaming the finding on contaminated meat in his native Mexico.

The Nevada Athletic Commission (NAC) 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 Alvarez] 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 [NAC] to decide if he was positive or negative. I was surprised this happened. Knowing Canelo and his team, I didn't expect they were using some kind of forbidden substances."

Alvarez 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 Alvarez, in September 2017, ended in a controversial draw.

Saunders is set to defend his WBO title against Martin Murray in London on April 14.