Palestinian militant groups have said they need more time to consider a proposal to suspend attacks on Israelis.
Israel says there should be no talks with militants
Hamas, al-Aqsa Martyrs' Brigade and Islamic Jihad are said to be close to a deal, which could be a crucial step forward for the international peace initiative known as the roadmap.
But their leaders suggested any breakthrough may not come before the weekend - contradicting earlier remarks by Palestinian leader Yasser Arafat that an announcement was expected "within hours".
The BBC's Barbara Plett in Ramallah says any ceasefire will be a unilateral move by the Palestinians as the Israelis continue to insist that militant groups are dismantled, not negotiated with.
We are still waiting for responses from our [fighters] in the field and also from those in Israeli prisons - we cannot do that in a few hours
In ongoing violence on Thursday, two Palestinians were shot dead by Israeli security forces as they were attempting to enter Israel from the West Bank, Israeli public radio reported.
And the al-Aqsa Martyrs' Brigade - linked to Mr Arafat's Fatah movement - killed an Israeli man near the Green Line between Israel and the West Bank.
Palestinian Prime Minister Mahmoud Abbas - better known as Abu Mazen - has been trying to secure agreement from the armed factions to suspend attacks on Israelis for a period of three months.
But correspondents say Mr Arafat continues to have a vital role to play with the militant groups and with the broader Palestinian public.
His comments, after a meeting with Ireland's foreign minister, were explicit.
Arafat remains influential
"Until now, it has not been officially decided, but we expect that in the coming few hours, there will be a declaration," he said.
Mohammad al-Hindi, a top Islamic Jihad official, said truce talks had been ongoing, but Mr Arafat's timetable was too optimistic.
"We are still waiting for responses from our [fighters] in the field and also from those in Israeli prisons. We cannot do that in a few hours," he said.
Asked when a truce announcement might be made, Mr Hindi said: "It is fair to say in the next few days."
Abdel-Aziz al-Rantissi, second-in-command of Hamas and himself a target of a recent Israeli assassination attempt, agreed that it would be days before a final decision was made, the AFP news agency reported.
Correspondents say that details may yet have to be worked out and the success of a cessation of attacks on Israelis is far from guaranteed.
A truce declaration could coincide with Sunday's scheduled visit to the Middle East by US National Security adviser Condoleezza Rice.
She and US Secretary of State Colin Powell have been personally charged by the president to promote the roadmap and do what they can to bring peace between the Israelis and the Palestinians.
Ending violence is a key first stage on the US-backed roadmap peace plan which promises security for Israel and a Palestinian state, but bloodshed continued on Thursday.