According to Israeli radio and Ynet, the website of the Yediot Aharonot daily, Sharon told his weekly cabinet meeting on Sunday that more preparations were needed if a summit was to yield any results.
"It is important to hold talks, but we cannot attend the meeting without adequate preparation," he was quoted as saying by Ynet.
His comments came as two of his top aides met senior Palestinian officials in Tel Aviv in a bid to iron out differences over the agenda.
Abbas told reporters on Saturday that he saw no point in holding a summit which was just a "public relations exercise".
Abbas and Sharon were to have met at the beginning of last week, but were then unable to agree on an agenda for the summit amid a spike in violence in the Gaza Strip.
With Israel due to come to a shutdown on Wednesday and Thursday as Jews mark the Yom Kippur day of atonement, and Abbas due to travel to the United States next week, failure to agree to a meeting on Tuesday could lead to a lengthy postponement.