Robinho was a £32.5million recruit by City in the summer of 2008, but, despite flashes of his class, the former Real Madrid player has not set the Barclays Premier League alight and is known to want a return to his homeland.
While City officials remain reluctant to discuss the issue and boss Roberto Mancini insists he wants the player to stay so long as he is happy, Robinho said he was "90%" certain he will return to Santos in the current window.
The sticking point may concern Robinho's weekly wages, which are well in excess of £100,000.
Santos communications co-ordinator Arnaldo Hase told BBC Radio Five Live: "We are respecting Manchester's directors, they have to be respected.
"We are optimistic without being too optimistic.
"The negotiations began last week, there were some mails between the Manchester directors and Santos directors.
"The Manchester directors agreed to the possibility of discussing the negotiation. Our marketing directors travelled to England on Saturday and arrived on Sunday.
"They are in London now and I think they are conducting the negotiations now."
Regarding the length of the possible loan deal, Hase said: "The first thought of the Manchester directors, it was about six months. Of course Santos would like it to be more - one year, one year and a half if possible."