A letter urging a complete ban on Russian athletes at next month's Rio Olympics has been leaked. It comes just before the World Anti-Doping Agency releases a key report on Monday into doping allegations at the 2014 Sochi Olympics.

A WADA board member says the leak has undermined the credibility of the report.

Currently, only Russian track and field athletes are barred from competing in Rio after a global competition ban on the All-Russia Athletic Federation.

Russia is challenging the ban at the Court of Arbitration for Sport, with the tribunal expected to conclude on Thursday.