On the eve of the club's League Cup semi-final second leg at Manchester United, Mancini said City were in talks with Robinho's former team Santos and Sao Paulo about a potential loan move.
"I think the big problem for him ... is there is a World Cup in June and he wants to play," Mancini told reporters.
"If he doesn't play it's a problem for the national team but I must decide what's best for my team in every game.
"I must decide between five or six strikers and it can be difficult for me and for him."
Mancini said he saw the long-term future of Robinho, who joined from Real Madrid in 2008 for a British record 32 million pounds, at City but would allow him to move on a temporary basis if the conditions were right.
"If everything is ok for me, for the club, for Robi, it's possible he will play for another team," said the Italian.
"Santos or Sao Paulo are possible but it's important that Robinho is happy, the club is happy and everyone is happy.
"Sometimes this is possible and it can happen. In Italy it's the same. You buy a fantastic player like Robinho for a lot of money and he needs to play for another club," added Mancini.
"It's important that everything is ok and if Robinho goes to another club he plays well and then comes back. But if he stays here, for me it's ok."
Mancini, though, said Robinho could still be in his squad when City look to preserve their 2-1 first-leg lead against United on Wednesday.
Striker Emmanuel Adebayor, who has not played since the deadly gun attack on the Togo team bus at the African Nations Cup in Angola at the start of the month, is likely to be on the bench at United.
