Palestinian chief negotiator Saeb Erekat, who led several rounds of peace talks with Israel, has told the BBC he has handed in his resignation.
Mr Erekat had previously promised to quit if it emerged that secret files recently leaked on the Middle East peace process had come from his office.
Meanwhile, an aide to Palestinian Authority leader Mahmoud Abbas said elections would be held by September.
Hamas immediately rejected the plan, saying Mr Abbas had no legitimacy.
"Hamas will not take part in this election. We will not give it legitimacy. And we will not recognise the results," spokesman Fawzi Barhoum said.
His mandate as Palestinian Authority President expired when elections planned for January 2010 were postponed because of disagreements between Hamas and Fatah, Mr Abbas' secular faction.
The last time the Palestinians voted, in 2006, Hamas emerged as the biggest winner in a parliamentary ballot.
Their success led to bitter splits within Palestinian politics that eventually saw Hamas take control of the Gaza Strip, while Mr Abbas' Fatah faction runs the West Bank.
The BBC's West Bank correspondent Jon Donnison says the election pledge seems intended to show that Palestinian leaders are responding to events in Egypt and Tunisia.
News that Saeb Erekat has offered his resignation could bring down the curtain on a lengthy career as a senior negotiator.
However, Palestinian leader Mahmoud Abbas has yet to accept his offer.
He was part of the team advising former Palestinian leader Yasser Arafat and was involved in peace talks throughout the 1990s.
Since Mr Arafat's death in 2004 Mr Erekat has led Mr Abbas' negotiation team, but seen little progress made with Israel despite a lull in violence.
The veteran negotiator has offered to resign on several previous occasions, only to stay in his position.
The latest resignation comes as negotiations with Israel remain stalled. A push for a permanent peace deal launched by US President Obama late in 2010 foundered over the issue of Israeli settlement-building shortly afterwards.
In January the al-Jazeera TV network released details of some 1,600 confidential documents detailing Palestinian negotiating positions.
The files suggested the Palestinians were ready to make big concessions, despite public claims to the contrary.
In response, Mr Erekat admitted some of the material appeared genuine, and said the release by al-Jazeera had put his life in danger.