Rio de Janeiro had originally pledged to reduce pollution in the notoriously fetid Guanabara Bay by 80 percent but officials confirmed in March that the target will not be reached.
Instead, they are now concentrating only on parts of the bay where sailing competitions will take place although they have insisted that these areas will be safe.
“We can see significant progress, at the same time we have asked the organising committee to convey our concerns with regard to the issues of the water quality we are still facing in Rio,” Bach told reporters.
“The IOC executive board is watching this situation very closely and we are expecting more information and more reports by the time of our next meeting, next month in Kuala Lumpur.
“We are approaching major test events in August and we all need to see progress in this regard.
“I’m not an expert in water pollution, we have to leave it to the experts to tell us what is achievable, and in which time frame.
“These experts are telling us it is still achievable to have these competitions in safe water conditions and we have been advised today from the local organising committee that this advice has not changed.”
Bach also urged 2020 Olympic hosts Tokyo to settle on plans for the National Stadium as soon as possible.
Last month, Japan’s sports minister Hakubun Shimomura said the stadium, the centre piece for the 2020 Olympic Games and 2019 rugby World Cup, should ditch its plan for a retractable roof to save money.
He added that he wanted around 35 percent of the seats at the 80,000 seat stadium to be temporary ones in another cost-cutting measure.
“This is an issue for the national government to deal with,” said Bach. “We think this issue should be solved as soon as possible because Tokyo has so much positive news to spread that we do not want a discussion about the stadium to overshadow the excellent progress being made,” said Bach.
“It’s in everyone’s interest not to have this dragging on, we are confident that the national government will find a solution pretty soon.”
The new National Stadium will be built on the grounds of the old, now demolished, one which was constructed to host the 1964 Olympics.
(Writing by Brian Homewood in Berne; editing)