(CNN) -- Manchester City manager Roberto Mancini wants to add to his squad during European football's January transfer window, but the Italian has revealed the English Premier League leaders must sell before they can recruit new players.
City could lose brothers Yaya and Kolo Toure for over a month when they fly out to join the Ivory Coast squad for the African Cup of Nations this weekend, and Mancini hopes to draft in cover for the key midfielder and his defensive sibling.
Despite being widely considered the richest football club in the world, the 2011 FA Cup winners must offload wantaway high-earners such as striker Carlos Tevez before being able to spend on new signings.
"I said two months ago that we could have a big problem in January because we have to play big games without Yaya," Mancini told reporters.
City have signed a host of big-name players since being taken over by Qatar's Sheikh Mansour bin Zayed Al Nahyan in 2008.
In the pre-season transfer window, City spent approximately $127 million on star names such as striker Sergio Aguero, playmaker Samir Nasri and fullback Gael Clichy.
But financial fair play regulations introduced by European football's governing body UEFA mean City must slash the club's wage bill, having announced losses of $307.8 million in November -- the highest ever recorded in English football.
The new rules are designed to stop European football clubs spending beyond their means, with sanctions imposed on clubs who break them.
Mancini suggested the absence of the Toures, combined with injuries to Italy striker Mario Balotelli and midfielder Owen Hargreaves and a suspension for England's Gareth Barry, could mean City cannot fill the seven-man substitutes' bench for Sunday's FA Cup third-round clash with archrivals Manchester United.
"It's better that we sell first. Maybe then we can then take in other players ... If we have strikers injured then we need to buy another at the moment I have one striker and two midfielders," the former Inter Milan coach said.
In addition to this weekend's Manchester derby, the Toures could miss up to five league games as well as the two-legged English League Cup semifinal against Liverpool.
Mancini has warned that a lack of strengthening in January could have a negative impact on the club's ambitions, with City three points ahead of neighbors United and seeking to win a first English title in 43 years.
"This could be the first championship for many years and we need to do everything we can to win it," the 47-year-old said.
"United and Chelsea have won trophies for many years. So they are quiet. They understand that they can play without pressure. For us it's different."
Sunday's match at the Etihad Stadium is a repeat of the 2011 FA Cup semifinal, which City won 1-0 through a goal from Yaya Toure en route to the club's first trophy in 35 years.