The vote is to take place the same day Palestinian foreign minister Riyad al-Malki addresses the assembly, the sources told AFP.
The United Nations Educational, Scientific and Cultural Organisation on Tuesday started holding its general assembly, which, like the UN General Assembly in New York, is to vote on Palestinian membership.
But while as a permanent UN Security Council member the US has a veto that it says it will exercise at the General Assembly, no one has a veto at UNESCO, where a two-thirds majority of its 193 voting members suffices.
Arab states braved intense US and French diplomatic pressure to bring the motion before the UNESCO executive committee earlier this month, which passed it by 40 votes in favour to four against, with 14 abstentions.
Palestine currently has observer status at UNESCO and diplomats told AFP that it would have no problem garnering the required votes to become a full member.
Such a move would automatically spark a crisis between Washington and UNESCO, as two laws passed by Israel's staunchest ally in the 1990s ban the financing of any United Nations organisation that accepts Palestine as a full member.
UNESCO stands to lose $70 million, or 22 percent of its annual budget.