WBA "regular" heavyweight champion Manuel Charr will not defend his belt next week against American challenger Fres Oquendo after a 'suspect' doping test by the Syrian forced the fight to be cancelled, his management said on Thursday.

Charr's A sample from an Aug. 31 test showed "two suspect substances" and due to time constraints regarding the opening and testing of the B sample the bout was now cancelled.

According to The Sun, Charr came up positive for anabolic steroids, epitrenbolone and drostanolone.

The testing was conducted as part of the WBA's random drug testing protocol, which like the WBC is run by VADA [Voluntary Anti-Doping Association].

Charr denied that he took any illegal substances voluntarily and claims that some form of contamination was must be the cause - and questionined why he would need performance performance enhancing drugs to fight a 45-year-old boxer with four years of inactivity.

"I cannot explain it and I am asking myself how could it happen," the fighter, who lives in Cologne, told the Koelner Express newspaper.

"I have never taken anything. I fought Vitali Klitschko and Alexander Povetkin, seven title fights and I was always a clean athlete. Why should I take something before the fight against Fres Oquendo."

The 33-year-old Charr (31-4) had won the WBA title against Russia's Alexander Ustinov last year.

Oquendo has not fought since losing a decision a decision to Ruslan Chagaev in July 2014. He would later win an arbitration order which forced another title shot. Oquendo was scheduled at one point to fight Shannon Briggs for the vacant WBA "regular" title, but that contest was also canceled after Briggs tested positive for a banned substance.