Andy Ruiz Jnr says he'll REFUSE to fight Anthony Joshua in the UK

Andy Ruiz Jnr has warned he will refuse to rematch Anthony Joshua in the United Kingdom as he fears a 'set-up'.

The Mexican shocked the world on June 1 when he stopped Joshua in the seventh round to become WBA, WBO, IBF and IBO champion of the world.

And reacting to the news of Dillian Whyte's alleged failed drugs test, Ruiz Jnr posted a tweet saying: 'I’m not going to the UK for the rematch #issasetup.'

Whyte reportedly tested positive 'for at least two banned substances' prior to Saturday's victory over Oscar Rivas.

The British Boxing Board of Control allowed the fight to go ahead according to legal protocol pending B sample tests and appeals. If Whyte's B sample is negative then he would be cleared of any wrongdoing.

But it seems Ruiz feels the fight should not have taken place with doubt over Whyte's tests.

He replied to a fan asking if he had genuinely been put off coming to the UK.

'At the end of the day I just want a fair playing ground. The fact that Rivas had no idea about it is a bit sketchy. I will and want to fight AJ next no ifs or maybes about that,' he clarified.

The 29-year-old later added: 'I love everyone’s passion for boxing on Twitter.

'I appreciate the people who can argue without insulting those are the people I will always reply to. It’s all love.

'Whether the fight happens in the UK or the USA it will be another epic fight. Night.'

Whyte claimed the interim WBC title in picking himself off the canvas to defeat his Colombian opponent on points at O2 Arena on Saturday.

He put himself in line to challenge Deontay Wilder in a hugely lucrative world title fight but if he is proven to have taken banned substances, that encounter is unlikely to take place, particularly following the American's lengthy tirade at the news.

'Bronze Bomber' took to Instagram, branding Whyte a 'cheat' and 'donkey of the year'.

Matchroom Boxing boss Eddie Hearn, who promotes both Whyte and Joshua, has a headache if Ruiz Jnr digs his heels in and refuses to fight in the UK.

Wembley or Cardiff's Principality Stadium have long been touted as the two most likely locations for what would be a career-defining fight for AJ.

The former Olympic champion was a massive favourite to cruise past Ruiz Jnr on his American debut at Madison Square Garden last month.

In the third round Joshua knocked his opponent down but then unravelled dramatically, hitting the canvas twice himself before the bell.

Disorientated and seemingly out of ideas against his smaller, faster opponent, Joshua continued to struggle and was knocked down twice more.

He spat out his mouthguard and failed to adequately respond to the referee's instructions, sparking wild celebrations from Ruiz Jnr who became the first Mexican heavyweight champion in history.

Ruiz had stepped in to take the fight on short notice after Joshua's slated opponent Jarrell Miller failed a drugs test.

And with some bookmakers offering odds as long as 25/1 on the underdog, few gave him a chance, but 'The Destroyer' is now in a commanding negotiating position and talks between the two camps are still ongoing.