Monday 20 June 2016 13:47, UK
Craig Reedie, the head of the World Anti-Doping Agency, says he would be prepared to back a total ban on Russia competing at the Rio Olympics.
The founding president of WADA, Dick Pound, told the Sunday Times newspaper that such a ban was "not impossible".
On Friday the International Association of Athletics Federations (IAAF) upheld an international ban on Russia's track and field competitors first imposed in November after a WADA team led by Pound revealed state-sponsored doping and mass corruption in Russian athletics.
The Russia team is now ruled out of all events in athletics in Rio, although Russian athletes training outside the country can apply to compete as neutrals at the August 5-21 event in Brazil.
The IAAF's decision was endorsed by the International Olympic Committee on Saturday.
But there are fears that the scale of Russia's breaking of doping rules extend beyond just track and field, with swimming said to be another sport that has broken doping rules.
In May, WADA set up a new investigation under Professor Richard McLaren, a Canadian law professor and longstanding member of the Court of Arbitration for Sport (CAS), into allegations of state-backed doping at the 2014 Sochi Winter Olympics in Russia.
McLaren, who is due to deliver his full report by July 15, said in a preliminary statement on Friday he had evidence that Russia's Ministry of Sport was involved in instructing a Moscow laboratory to "not report positive sample results over the period before, during and after" the 2013 World Athletics Championships.
Reedie, speaking at a WADA conference at Lord's cricket ground in London, said: "In the coming weeks, we will learn the outcome of our independent McLaren investigation.
"If his report indicates transgressions of any kind, then there will be a precedent-setting opportunity to demonstrate our collective commitment to cleaning up sport. The world will be watching."
Asked if a blanket ban on the Russians for Rio was a realistic proposition, Reedie said: "I think Dick called that the 'nuclear option'.
"I can't answer that question because I don't have full information and I await to see what happens at the Olympic summit (in Lausanne) tomorrow (Tuesday), when those authorities who do have that power to make those decisions will presumably be discussing them.
"WADA does not have the power to determine which sports do what. If McLaren produces detailed corroborative evidence that goes beyond athletics, we are concerned...we will respond firmly and effectively."
