Hamas chief Khalid Mashaal and his deputy Mousa Abu Marzouq updated Shaath on talks in Cairo between Palestinian factions and an Israeli delegate.
Fatah leader and President Mahmoud Abbas is also in direct contact with Mashaal, Shaath said.
Shaath told Ma'an that a ceasefire "is not likely to take effect in the coming days because Israel is trying to impose its own stipulations ignoring the demands of Hamas and other Palestinian factions."
Palestinian factions are demanding an end to Israel's siege on Gaza and that Israel stops all incursions into Gaza, stops assassinating leaders and stops firing at fishermen off the coast.
Shaath said Israel initially requested that Hamas hand over all its weapons. Hamas refused, and said it would agree to stop targeting civilians in a ceasefire.
Turkey and Qatar are playing a major role in the negotiations sponsored by Egyptian President Muhammad Mursi, according to Shaath.
Asked about guarantees that Israel would not violate a possible ceasefire agreement, Shaath said "the only guarantee is the other side's commitment.
The latest offensive began on Wednesday when Israel broke an Egypt-mediated ceasefire by assassinating Hamas military commander Ahmad al-Jaabari.
Since Wednesday, Israel has killed 73 Palestinians and wounded hundreds more in the Gaza Strip. Three Israelis have been killed by a rocket fired by militants in Gaza.
Mashaal told Shaath that Hamas is ready to resume reconciliation talks with the Fatah-led Palestinian Authority as soon as the offensive on Gaza is over. The Hamas chief has asked Egypt to host unity talks in Cairo to implement earlier agreements.
Shaath is scheduled to visit Gaza on Monday at the request of Abbas to show solidarity and meet with faction representatives.
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