LONDON (AFP) - Everton chairman Bill Kenwright revealed on Thursday that the Premier League club have rejected a transfer request from Chelsea target John Stones.

Stones earlier this week formally expressed his desire to quit Goodison Park as he tries to force through a move to Premier League champions Chelsea before the transfer window closes on Sept 1.

The 21-year-old is reported to be frustrated that Everton have rejected a third bid of around £30 million (S$65 million) from Chelsea.

But his request to leave was snubbed by Everton manager Roberto Martinez, with Kenwright releasing a statement that emphasised their determination to hold onto the highly-rated England international.

"Everton Football Club has rejected a transfer request from John Stones," Kenwright said on Everton's website.

"Since the start of the transfer window, we have resolutely turned down offers from another Premier League football club for our player.

"John is not for sale and he will remain a highly valued member of our first team squad."

Martinez insists he has big plans for Stones and has maintained his position that the centre-back is not for sale.

Despite Stones asking to leave, Martinez is confident he can not only keep hold of a prized asset but persuade the player he has a vital role to play going forward.

"During this tough period we are going to be there for him," Martinez said.

"We have great ambition, desire and great plans for John. We want to be a winning team and we need to keep our best performers and clearly John is a big part of our future.

"We are a big football club with an incredible tradition and we will carry on giving him everything we can.

"As a young man you are under massive pressure and you are going to get influences.

"We are going to look after John. We are going to understand him."