Writing in The Times newspaper, the champion leg-spinner said he had no specific plans on his future career after retiring from Test cricket at the end of Australia's 5-0 whitewash of England last week.
He admitted that the lure of the commentary box was "very attractive" but would love to stay in the game, preferably helping the Aussies remain at the top of the world game.
"Beyond that, I also want to make sure that cricket stays healthy worldwide. So I would not have a problem helping in England, New Zealand, South Africa or anywhere else," he added. "We live on a small planet these days."
But Warne, who admitted it was "strange" to refer to himself as "Shane Warne, the former Test cricketer", said he had received no specific request from Fletcher or the England and Wales Cricket Board (ECB).
Warne, who bowed out having taken 708 Test wickets -- 195 of them against England -- said he retained a great affection for England, having played in the English league for Hampshire.
During his time there, he said he had helped a number of England bowlers informally, while England spinner Monty Panesar had sought his advice after the Fifth Test in Sydney last Friday.
"Of course, there is a big difference between an informal chat, where you wouldn't dream of asking for a cent, and actually being employed," he wrote.
"I am not sure what Duncan has in mind, whether it is for me to go around the counties or for bowlers to come to see me at Hampshire.
"As a general comment, if I could help the cause of spin bowling, if I have the time and if it fits in with my family, then I would give it a lot of thought... Whatever I do, I want to do it properly."
Fletcher, who is under fire in the aftermath of England's under-par performance in the Ashes, raised the prospect of Warne crossing cricket's great divide on Friday.
"I'd be happy with him to speak to anyone, there's no doubt about it," he told reporters in Sydney.