Ms Aitken said the pandemic has had a “significant impact” on the city’s cleansing services but she insisted the litter situation is improving.
She was speaking after the issue was raised on the BBC’s Question Time programme on Thursday night, with audience members voicing concern about how the city will look as it hosts world leaders in November.
Refuse workers in the city are set to go on strike during the international conference if a pay dispute is not resolved.
Speaking on BBC Radio Scotland’s Good Morning Scotland radio programme on Friday, Ms Aitken said: “We’re very clear that the pandemic has had a very significant impact on our cleansing services.
“The recovery from that is coinciding with Cop26, but the recovery from that actually is moving at pace.”
She acknowledged some parts of the city have “particular issues”.
Ms Aitken said: “We’ve had teams out in recent weeks, focusing on issues of fly-tipping, where there are problems with commercial waste in the streets, and we are seeing a difference there.
“A lot of this is about behaviour of course, and the council has to respond to that behaviour.
“But we also need for people to try and change their behaviour, you know, it’s not the council that’s fly-tipping.”
Ms Aitken, who leads the council’s SNP administration, said she is still confident the city can be “spruced up” and looking great by the time of the summit.
She continued: “There are still some spots, hotspots, where we have particular challenges that are largely down to issues like fly-tipping.
“Environmental crime, to be honest, is what we’re having to respond to.”
She urged residents to report any fly-tipping incidents where they see them.
Saying Glasgow’s cleansing services are getting back on track, Ms Aitken added: “According to Keep Scotland Beautiful, Edinburgh actually had much worse problems with litter throughout the pandemic.
“And nobody said that they shouldn’t have the Edinburgh International Festival.”