Brazilian media reported the former World Player of the Year and World Cup winner had already accepted the invitation.
Ronaldo was approached by Brazilian Football Confederation (CBF) President Ricardo Teixeira, also head of the LOC, to take on an important role without this meaning Teixeira would step down from the latter position, the source said.
"Ronaldo was sounded out and now things are on course towards a decision in the coming days," said the source, on condition of remaining anonymous.
"After a more political preparation stage, including the choice of the city venues among other things, now it's time for another person to take on the role at the front of the committee."
The 64-year-old Teixeira, who has led Brazilian football since 1989 and is also a member of world football body FIFA's ruling executive committee, is being investigated by Brazil's federal police on suspicion of corruption and money laundering.
He denies the allegations against him but the matters have raised questions about his suitability to remain in charge of organising the World Cup tournament.
Bringing in the 35-year-old Ronaldo, who since retiring from football in February has become a successful sports businessman, would put a football man of unimpeachable qualifications in and outside Brazil in the front line of World Cup preparations.
IMMINENT APPOINTMENT
Brazilian newspaper websites said Ronaldo, who was voted three times the world's best player and is the World Cup's all-time leading scorer, would officially be unveiled in his new role at a news conference in Rio on Thursday.
"Ronaldo will be the organisation's strongman, the voice and image of the 2014 Cup along with the city venues, (federal, state and city) governments and FIFA," O Estado de Sao Paulo reported on its website.
The CBF said Teixeira would hold a news conference on the same day on his return from a trip to Europe but gave no details.
A spokeswoman for Ronaldo told Reuters she had nothing to say on the matter and the man himself, approached by reporters when he visited Formula One's Brazilian Grand Prix in Sao Paulo on Sunday, denied he had received an invitation from the LOC.
The arrival of a former player on the committee preparing the 2014 World Cup would repeat in Brazil what happened in France in 1998 and Germany in 2006 when ex-national team captains Michel Platini and Franz Beckenbauer ran their countries' World Cup tournaments.
Pele, Brazilian football's greatest player, does not get on with Teixeira and is not involved in the LOC, but he was named by Brazil's President Dilma Rousseff as a Cup special ambassador - a move seen as rebuff of Teixeira.
She has effectively frozen Teixeira out of Brazil's negotiations with FIFA and made it clear to FIFA executives, including general secretary Jerome Valcke, that she does not have confidence in Teixeira, an official with knowledge of the talks told Reuters recently.
Teixeira's critics say his role as the face of the
