Bach and other Olympic officials said the construction holdups and political paralysis have reached a critical point, requiring the IOC to take special measures to save the games.
"It is about time for action," Bach said following an unprecedented venting of criticism and complaints from international sports leaders about the lack of progress in Rio.
"We share their concerns," he added. "We will address them. We will do everything we can do make these games a success."
Bach said the International Olympic Committee executive board would meet later Wednesday to discuss the Rio situation and decide on what action to take. He did not say what steps might be implemented.
Several sports federations asked about "Plan B" contingencies for their venues and one — handball — asked if there was a backup for the games themselves if Rio won't be ready on time.
Without completely ruling out moving the games out of Brazil, the IOC and other Olympic officials made clear they expect the games to take place in Rio but the timelines are extremely tight.
"If action is taken now, then we can deliver and Rio can deliver," said Gilbert Felli, the IOC's executive director of the Olympic Games.
Leaders of 18 different federations spoke out about Rio's troubled preparations in a meeting with Bach and the IOC board. All but one — volleyball — raised serious concerns.
"The general feeling is that we are in the most critical situation in the preparation for the games that has happened in the last 20 years at least," said Francesco Ricci Bitti, head of the Association of Summer Olympic International Federations.
Ricci Bitti said the sports raising the issue of a "Plan B" were referring to venue plans, not moving the games.
"We are not at this stage," he said, adding that basketball, for example, could consider playing some games in Sao Paolo if the Deodoro venue won't be ready.
The Italian urged Bach to make another trip to Brazil soon to meet with government leaders and organizers. Bach travelled to Brazil in January for talks with President Dilma Rousseff.
Bach told the delegates Wednesday that he had told Rousseff there was "not a single day to lose," and that the IOC's co-ordination commission for Rio warned organizers last month there was "not a single hour to lose."
Bach said he was waiting for more details of Tuesday's meeting in Brasilia between Rio organizers and Rousseff's chief of staff. Brazil's sports ministry said the deadlines would be met "and the games themselves would take place without disorder."
Bach noted that the IOC will be sending several task forces — made up of groups of experts in various fields — to Rio to monitor the situation. Felli will be assigned to work with Rio when he steps down from his IOC position later this year.
Ricci Bitti said the Olympic project is in danger of falling further behind because of the upcoming World Cup in Brazil and presidential election in October.
"We require you to take action immediately," the Italian told Bach. " We cannot waste these next six months."
The greatest concerns centre on the Deodoro complex, an area that is to host venues for eight sports — shooting, equestrian, modern pentathlon, canoe-slalom, rugby, basketball, cycling and field hockey. Work has yet to begin on the site.
"We believe it might be prudent to consider contingency plans if things do not progress," hockey federation director general Kelly Fairweather said.
The eight sports with planned events in Deodoro met later Wednesday with Rio organizers, and the Brazilians reported "constructive dialogue on venue timelines." Rio confirmed the tender for Deodoro would be released this month.
Federations expressed worries not only about construction delays, but also over accommodations, transportation and water pollution.
Speaking out were leaders of equestrian, field hockey, badminton, rugby, tennis, sailing, triathlon, basketball, athletics, cycling, rowing, modern pentathlon, gymnastics, archery, golf and handball. Volleyball, which has an existing indoor venue and will use the Copacabana for beach volleyball, was the only one that said it was satisfied.
Jose Perurena, head of the international canoe federation, said he would give Rio a "red card." Basketball asked about moving some games to other Brazilian cities; rowing noted that some fish are dying from lack of oxygen at its polluted venue; sailing asked for medical experts to study the pollution in Guanabara Bay; and golf said it would have to look at "Plan B" if the new course remains way behind schedule.
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