Maurizio Sarri believes Chelsea need to overturn their two-window transfer ban to be able to catch Premier League pace-setters Manchester City and Liverpool next season.

Chelsea will take their fight against FIFA's two-window transfer embargo to the Court of Arbitration for Sport (CAS), with head coach Sarri admitting the Blues will struggle to chase next term's league title without new recruits.

The Premier League club "categorically refutes" FIFA's latest findings, after the game's governing body rejected the Blues' appeal against the transfer embargo for signing underage players.

Chelsea were fined £460,000 for 29 breaches of the international transfer rules on minors, and FIFA threw out the Blues' appeal on Wednesday.

"It's very difficult to cover the gap at the moment; we need to work, probably we need to do something from the market," said Sarri, with third-placed Chelsea 24 points behind league leaders City and 23 behind Liverpool.

"So it's not easy, because the level of the top two is very, very high – as we can see in Europe, so it's not easy.

"Of course we have to work and we have to try. In my opinion we can reduce the gap.

"I don't believe when you buy 10 players, I think that we have to buy only one, two players. Otherwise it's very difficult to improve immediately.

"I think we are a very good team so we need only one, two players, no more."

Chelsea will host Eintracht Frankfurt in Thursday's Europa League semi-final second leg at Stamford Bridge, with N'Golo Kante missing due to hamstring trouble.

FIFA confirmed it has "partially upheld" Chelsea's appeal, but only in allowing Chelsea to sign European players aged under 16.

The ban on signing over-16s and the fine remain in place, leaving Chelsea hugely frustrated.

The Blues will now hope CAS will force a suspension of the ban pending another appeal, but FIFA will likely be in opposition.

Real Madrid continue to fight to prise Eden Hazard away from Chelsea this summer, with Chelsea understood to be holding out for a £100million fee for their Belgium talisman whose contract expires next summer.

Chelsea's statement read: "The club is very disappointed that the transfer ban of two consecutive registration periods was not overturned.

"Chelsea FC categorically refutes the findings of the FIFA Appeal Committee. It acted in accordance with the relevant regulations and will appeal the decision to the Court of Arbitration for Sport (CAS)."