Hamas chief Khaled Meshaal on Monday called for "national unity" but said a first congress among Palestinian leaders in 20 years should be postponed until a compromise is struck.
Meshaal, speaking in Qatar where he lives in exile, said Palestinian leaders from the Islamist movement Hamas and the secular Fatah had to present a unified front.
"We as Palestinians, we are being divided against ourselves; there's a lack of authority," he told a news conference in Doha.
"It's unbelievable and it's unacceptable from any Palestinian leader."
He added: "The cause of Palestine is bigger than Hamas and Fatah."
But Meshaal said a proposed congress of Palestinian leaders set to take place later this month should be postponed.
"Postpone the meeting of the National Congress until there's a compromise for the meeting," he said.
"The meeting should be about the laws and regulations we agreed on otherwise this will lead to more division."
He added that Hamas were ready to meet its rival Fatah "in any Arab country".
Earlier on Monday, Palestinian leaders moved toward a postponement of the congress amid speculation over the intentions of president Mahmud Abbas.
The meeting of the Palestine National Council, a congress representing those in the Palestinian territories and the diaspora, was to take place on September 14-15 but a new date is likely to be set.
Abbas has announced his resignation as chairman of the Palestine Liberation Organisation in a bid to force new elections for its executive committee.
Abbas's allies say his moves are part of efforts to inject new blood in the Palestinian leadership.
Critics, however, argue that Abbas is manoeuvring to empower his allies and marginalise opponents ahead of the 80-year-old's eventual retirement.