Sources close to Hamas said that the movement has agreed to release Shalit in return for "several hundred" Palestinian prisoners.
However, the sources denied reports that Hamas and the two other groups that are holding Shalit were demanding only 450 prisoners. They predicted that Shalit will be released "within days."
"The number will be much higher," the sources explained. "In addition to 450 prisoners, Israel will also release all minors and female prisoners, but this will happen in stages. The women and minors will be released before Shalit is handed over to the Egyptian authorities."
A top Hamas official in the Gaza Strip told The Jerusalem Post that jailed Fatah leader Marwan Barghouti was on the top of the list that was presented to the Egyptians and Israelis.
"If all goes well, Marwan will be released within days," he said. "Our understanding is that Israel has agreed to release many senior Hamas and Fatah activists. We are now waiting for the results of Thursday's summit between [Egyptian] President Hosni Mubarak and [Prime Minister] Ehud Olmert."
The official revealed that the breakthrough in the negotiations over the release of Shalit was achieved last week during a secret meeting between Syria-based Hamas leader Khaled Mashaal and Egyptian Intelligence Chief Omar Suleiman in Saudi Arabia.
Shalit's captors claimed Tuesday that "significant progress" had been made in the last few days toward reaching a prisoner exchange agreement with Israel.
Abu Mujahed, spokesman for the Popular Resistance Committees, an alliance of various armed Palestinian groups in the Gaza Strip, said Egyptian mediators have come up with an offer "that is close to our demands."
He said the three groups that are holding Shalit have decided to form a joint committee to study the Egyptian offer and work toward bringing about a prisoner swap with Israel.
"We are hoping that this case will come to an end very soon," Abu Mujahed said. Asked if a prisoner deal could be struck before the weekend, he said: "The ball is now in Israel's court. We are waiting for a positive response from Israel. If Israel does not accept the Egyptian offer, we are ready to hold on to the soldier for years."