The deadline is thought to have been set in an effort to see a takeover completed by the middle of November with current owner Mike Ashley wanting in the region of £300 million for the club.
BBC Sport reported: “It’s hoped that Tuesday will be a significant day in the sale of the club.
“Interested parties who wish to buy Newcastle have been asked to make their intention clear by Tuesday as to whether they intend to make a serious bid for the club.
“If there are serious buyers who emerge by Tuesday, the sale could then be completed by the middle of November.”
The unexpected departure of manager Kevin Keegan prompted Ashley to put the club up for sale as he and Dennis Wise came under intense abuse and criticism from Newcastle fans. Ashley, however, insists he will hold off for the right price.
A dossier has been handed out to all interested parties explaining what buying the club would involve. All parties have also been asked to sign a confidentiality clause.
Interest is rumoured to be coming from South African businessmen, a Nigerian consortium, America and the Far and Middle East.
Meanwhile, Michael Owen has cast doubt on his future at the club by holding off contract talks until the current turmoil within the club is resolved.
His four-year contract will come to an end next summer and whether he will remain at the club is still unclear.
Owen said: “We began negotiations at the start of the season, but with all that has been going on we haven’t spoken for a while.”
Newcastle were reported to have offered Owen a three-year deal at the end of August, but his representatives insisted that only a one-year extension was offered - which would also involve a £15,000-a-week pay cut.