The 29-year-old, who is wanted by Sunderland among others, has a year remaining on his current deal and the Swans do not want to lose him.
His representative, Jamie Moralee, told the South Wales Evening Post: "At the moment, there have been some bids coming in
Swansea have rejected those because they think Ash is important - everyone's clear on that
"Swansea are very clear that Ashley is not for sale
Whatever offer comes in, he is not going to be sold.
"That's the option they've got and we're comfortable with that
We respect that because he's their player, he's under contract."
Moralee admitted Swansea could cash in on Williams now or allow him to leave the Liberty Stadium for nothing in a year's time, but indicated that an extended stay at the Liberty Stadium is his preferred option.
He added: "If Ashley signs another contract at Swansea, he will probably end his career there
I'd like to think we can reach an agreement because that is Ash's preferred option."
Sunderland have registered their interest in Williams, to date with little encouragement from his current employers, but Moralee believes the Black Cats will not allow the matter to rest.
He said: "Sunderland have made it clear that they will just keep bidding and bidding
They want the player and I understand that
"Sunderland are trying to get their business done early, while others prefer to wait
It's too early for a big decision, but the transfer window has only just opened
Hopefully things will move along in the next week or so."
Source : PA
Source: PA