Mokoena is yet to return to training following South Africa’s World Cup exit.
The 29-year-old was expected to return for training on Friday.
“I spoke to Aaron on Monday night. He phoned me to ask if he could come back a bit later,” Cotterill told the Portsmouth News.
“He was meant to be back today, but wanted to know if he could have a bit more time off.
“Aaron has been in a lot of demand in South Africa due to his role in the team and the World Cup. He’s not stopped.
“He’s also getting married at the weekend, so I’ve said he can have a bit of extra time off.
“It’s not a problem. Aaron is absolutely fantastic, an absolute gentleman and someone I definitely want to stay. We are going to start having discussions with his representatives about him staying.
“I don’t want him going anywhere else.
“We’ll see what happens with the talks but I want him to stay.”
“At this rate, by Christmas Aaron will be dead on his feet,” he added.
“That’s something nobody wants to happen and we have to bear that in mind.
“We’ve got to look after him a bit and that is why he’s been given extra time off.
“He’ll now be back when we return to the UK after our pre-season in America.”