Zoughbi Zoughbi, a long-time Fatah member and activist, called the conference a "historical moment".
"It symbolises the will of the Palestinian people to lead themselves into self-determination and statehood," he told Al Jazeera.
While Fatah hopes the conference will rejuvenate the movement, officials denied that members would revise the group's founding charter which, like that of Hamas, calls for the Israel's destruction.
"It will remain as is. It won't be subject to discussion," Azzam al-Ahmad, a senior Fatah leader, said.
The charter calls for armed struggle "until the Zionist entity is wiped out and Palestine is liberated".
But a draft of Fatah's new programme calls for new forms of resistance such as civil disobedience against the expansion of Jewish settlements and the separation barrier, which Israel says is for security, but which Palestinians denounce as a land grab.
The movement, founded in 1965 by Yasser Arafat, the late Palestinian leader, is backed by the West because of its willingness to negotiate with Israel.
Peace talks with Israel have stalled for months and Abbas has said they will resume only if Israel freezes all settlement building, as called for by a US, European and UN-backed peace plan.
'Security and peace'
Speaking to delegates on the eve of the congress, Abbas said: "We hope that our neighbours will allow us to reach to peace, to build the future of our state that lives next to their state in security and peace."
Palestinian analysts have said Fatah would find it hard to compete with Hamas if it amended its charter before reaching any deal with Israel to establish an independent Palestinian state.
Fatah has been struggling to regain the dominance it enjoyed for decades before losing a 2006 parliamentary election to Hamas.
Hamas, which effectively rules the Gaza Strip, has refused to allow Fatah delegates based in Gaza to attend unless Fatah releases hundreds of Hamas activists detained in the West Bank.
Fatah member Zoughbi told Al Jazeera that it was "a shame" to convene the conference without the Gaza-based delegates
"Despite of all of that, I feel there is a message to convey to the whole world, that the Palestinian people are dedicated to the peace process," he said.
"Despite all the awkwardness and despite all the Israeli politics and policies in the occupied territories."
Fatah's congress aims to elect a new central committee and a ruling council, in the hopes of giving more of a say to a younger generation that grew up fighting Israel's occupation of the West Bank.
The last Fatah congress was held in Tunis in 1989.