Robinho was a £32.5m recruit by City in the summer of 2008, but, despite flashes of his class, the former Real Madrid player has not set the 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 yesterday said he was "90pc" certain he will return to Santos in the current transfer window.
The sticking point may concern Robinho's weekly wages, which are well in excess of £100,000.
Santos communications co-ordinator Arnaldo Hase last night said: "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."
Robinho said: "It's all on the right track. Santos are looking at the duration of my loan.
"Santos want a year, but City want just six months.
"It's 90pc certain. In two or three days it should be sealed."
Reports suggest Robinho is set to take a pay cut to move back to Santos, with City agreeing to pay at least part of his wages.
Santos president Luis Alvaro Ribeiro has also revealed the deal could allow the Premier League outfit first refusal on talented youngsters Paulo Henrique Ganso and Neymar.
Ribeiro said: "They want the first choice to buy the two boys. That does not bother us because we will sell the players for the best offer. If City have the conditions to match the offer, they can have the players."
City expect to have defender Kolo Toure back fit for tomorrow's Carling Cup clash against city rivals United, although Togo international Emmanuel Adebayor is not expected to figure after returning from a period of compassionate leave.