The show’s executive supervisor Jon Ola Sand told a press conference that the pop superstar has never been confirmed to perform and negotiations are ongoing, just days before the event.
It comes after Madonna’s publicists said last month that the 60-year-old will perform two songs at the contest on Saturday during the interval.
Mr Sand said: “It is true that we the EBU (European Broadcasting Union)… has not confirmed Madonna as an act for the Eurovision Song Contest.
“For the simple reason that we do not have a signed contract with her team and if we do not have a signed contract, she can not perform on that stage.
“So we are negotiating now, we are in the final stage of that but if there is no signed contract this week, she will not be on the stage.”
Mr Sand said previous reports about Madonna’s Eurovision performance were “rumours” and people had spoken out “without being authorised to speak on behalf of the EBU”.
It was claimed Madonna’s performance at the contest was expected to cost around $1m (£765,000), which would be covered by billionaire businessman Sylvan Adams.
There have been calls from some musicians for a boycott of this year’s Eurovision Song Contest over Israel’s alleged human rights abuses.
But Madonna, who has performed in Israel before, has rejected those demands, saying she she will “never stop playing music to suit someone’s political agenda”.
She said: “My heart breaks every time I hear about the innocent lives that are lost in this region and the violence that is so often perpetuated to suit the political goals of people who benefit from this ancient conflict.”
The Boycott, Divestment and Sanctions (BDS) movement has accused Madonna of “artwashing” abuse and urged her to cancel her performance.
This final of this year’s competition is taking place in Tel Aviv after it was won by Israeli artist Netta last year.