It rejects the document written by Palestinians, including some of its own resistance fighters, in Israeli jails.
Abbas had set a deadline for Hamas to accept the manifesto on Palestinian statehood by Tuesday. But the extension does not mean that his determination to go ahead with a vote has lessened.
The Palestinian president is well aware that a referendum would also be seen as a confidence vote on the Hamas government, which Israel, the European Union and United States boycott over its anti-Israeli stance.
Another PLO executive committee member said on Tuesday that there would be no need for a referendum should Hamas accept the blueprint at any stage before polling day.
Rawhi Fattuh, the former parliament speaker, said: "The referendum is not itself a goal. It's a way to break the isolation imposed on the Palestinian people."
There is little expectation, however, that Hamas will change its tune, although a new poll indicated that most Palestinians back Abbas's call for a referendum and intend to vote in favour.
A survey released by Birzeit University in the West Bank indicated that 77% of Palestinians intend to vote in favour of the blueprint and that electoral support for Hamas had fallen by 13%.
Ismail Haniya, who heads the Hamas government, said on Sunday that Abbas was not authorised to call for a referendum under the constitution and that polling the Palestinians so soon after the January elections was unnecessary.
But Haniya appeared cornered on Tuesday with mounting pressure from Abbas and his foreign allies.
Abbas is supported by Western powers that cut aid to the Hamas government, leaving the Palestinian economy in tatters.
Hamas urges talks
Haniya greeted the passing of the deadline with a call for more negotiations.
"We must continue the dialogue as it is the only way to resolve our differences and put an end to the Palestinian crisis," he said shortly after the PLO's decision
"We cannot accept that the dialogue has failed. We cannot decide this after just one or two additional meetings as there are many strategic questions to be addressed."
The president's blueprint calls for a national unity government, an end to attacks in Israel and the creation of a Palestinian state alongside Israel on land it seized by force in 1967, including Arab east Jerusalem.
Israel, however, claims the whole of Jerusalem as its "eternal and undivided capital" and has announced plans to set its borders unilaterally, claiming parts of the occupied West Bank for ever.
Israel has not commented about the idea of a referendum.
An official in the office of Ehud Olmert, the prime minister, said that it was an internal Palestinian affair. "Any sign of interference on our behalf could rebound on us and Abu Mazen," he said, using Abbas's nickname.
A popular endorsement of Abbas's blueprint would undercut Hamas's platform of refusing to recognise Israel and renounce its armed resistance against it.
It would also bounce Hamas into a coalition government with Fatah.
Sami Abu Zuhri, a Hamas spokesman, earlier called the referendum a "manoeuvre" to undermine the government's legitimacy.
Hamas's leaders in exile, meanwhile, said they were willing to hold talks with Fatah to end the deadlock after Yemen renewed an offer to host a meeting.
The invitation came from the Yemeni president, Ali Abdullah Saleh, who supports a negotiated peace deal for the Middle East, and was welcomed by Moussa Abu Marzouk, Hamas's deputy politburo chief.
"We don't know if Fatah has accepted, but Hamas is ready to hold talks in Yemen at the highest level," said Abu Marzouk who is a member of Hamas's exiled leadership in Syria.
"We are ready to travel to Yemen immediately once Fatah agrees on holding the talks."