Rio has not finalised its budget for the Olympics as well as the venues for several sports, including rugby, hockey and golf.
Rio organisers said last month the Sao Januario Stadium, home of football club Vasco da Gama, had missed the October 31 deadline and they would therefore revisit plans for the Joao Havelange Stadium to host the rugby sevens tournament instead.
"Our message remains but time is ticking. They (Rio organisers) need to carry on attacking this one with all vigour," IOC spokesman Mark Adams said.
Brazil is also hosting the 2014 World Cup and organisers for that event have also been urged to speed up preparations by world football's governing body FIFA.
Adams said the IOC Executive Board also asked organisers about the state of the country's economy with new figures showing lower than expected growth.
Brazil's economy posted extremely disappointing growth in the third quarter, piling pressure on President Dilma Rousseff to make deeper structural reforms and adding to fears that the global slowdown is hurting big emerging markets.
The economy grew just 0.6 per cent from the second quarter, government statistics agency IBGE said on Friday.
Rio, which was was awarded the Games in 2009, is the first South American city to be picked to host the Olympics.