By Mitch Phillips

LONDON (Reuters) - The International Olympic Committee's (IOC) president Thomas Bach will hold a media teleconference at 1400 GMT, when he is expected to announce whether Russia will be banned completely from the Rio Olympics.

The IOC's executive board met by teleconference on Sunday and is set to deliver one of the most momentous decisions in its history.

The board delayed a decision last Monday, saying it needed to look at legal options, but the path to a blanket ban appeared to open up on Thursday when the Court of Arbitration for Sport (CAS) upheld the International Association of Athletics Federations' ban on Russia's track and field team.

The CAS ruling underpinned the concept of punishing the innocent along with the guilty as sport's governing bodies wrestle with how to confront a sophisticated and widespread doping and cover-up system that involves athletes, anti-doping officials and senior government officers.

The IOC gave an indication of its outrage when it announced that disciplinary proceedings would be opened against Russian officials mentioned in the World Anti-Doping Agency's (WADA) independent McLaren report unveiled on Monday.

The report described extensive doping and cover-ups across a series of summer and winter Olympic sports and particularly at the Sochi Winter Olympics hosted by Russia in 2014.

The IOC said on Monday that it would not organise or give patronage to any sports event in Russia, including the planned 2019 European Games, and that no member of the Russian Sports Ministry implicated in the report would be accredited for Rio.

It also ordered the immediate re-testing of all Russian athletes who took part in the Sochi Olympics, as well as a full inquiry into the doping cover-ups. It instructed all international Olympic Winter Sports Federations to halt preparations for major events in Russia.

The IOC said it would "explore the legal options with regard to a collective ban of all Russian athletes for the Olympic Games 2016 versus the right to individual justice".

Since then a series of international sports federations, anti-doping agencies and athletes have spoken out to demand a blanket ban of all sports at Rio, though some have said they are against punishing innocent athletes.

Such a ban would be humiliating for Olympic superpower Russia.

Russian officials and government officers have said that the potential ban is part of a Western conspiracy and are likely to react with outrage if the IOC shuts them out.

President Vladimir Putin has said the affair could split the Olympic Movement, bringing echoes of the 1980s when the United States led a political boycott of the Moscow Games of 1980 and the Soviet Union led an Eastern Bloc boycott of the Los Angeles Games four years later.

(Editing by Clelia Oziel and David Goodman)