The 81-year-old leader was re-elected head of Fatah as the congress opened on Tuesday, but speculation has mounted over who will eventually succeed him as Palestinian president. He has not publicly supported a successor.
His speech is expected at 6:00 pm before some 1,400 delegates in Ramallah.
It comes with Palestinians facing continued Jewish settlement building in the occupied West Bank and an incoming Donald Trump administration in the United States seen as far more friendly to Israel.
More than 600,000 Israeli settlers now live in the West Bank and east Jerusalem, which the Palestinians see as their future capital.
The United States, European Union and others have warned that continued settlement building is eating away at prospects for a two-state solution to the conflict, the basis of years of negotiations.
A controversial Israeli bill to legalize some 4,000 settler homes in the West Bank had been due to come up for a first reading in parliament on Wednesday, but there were suggestions it was being delayed as further discussions occurred.
The international community largely considers all Israeli settlements in Israeli-annexed east Jerusalem and the West Bank to be illegal, whether they are authorized by the government or not.
The Israeli government differentiates between those it has approved and those it has not.
The progress of the bill, approved earlier by a committee of ministers on behalf of the government, has demonstrated the power of the settler movement in Israel.
Fatah's five-day congress is expected to discuss whether to seek to introduce a UN Security Council resolution against Israeli settlements.
Abbas, head of Fatah, the Palestine Liberation Organization and the Palestinian Authority since Yasser Arafat's death in 2004, has consistently called for a negotiated solution and opposed another violent insurrection.
But he has grown unpopular, with polls showing most Palestinians want him to resign and many losing faith in the so-called peace process spelled out in the Oslo accords of the 1990s, which he had helped negotiate.
Some analysts see the congress as an attempt by Abbas to marginalize political opponents, including longtime rival Mohammed Dahlan, currently in exile in the United Arab Emirates.
Observers have seen the reduced number of officials to vote—down from more than 2,000 in 2009—as part of a move to exclude Dahlan supporters.
The election of members of Fatah's parliament and its central committee will signal the direction the oldest Palestinian party will take.
The congress also comes with Fatah and its Islamist rival Hamas, in power in the Gaza Strip, still deeply divided. Fatah dominates the Palestinian Authority, which runs the West Bank.
However, a letter from exiled Hamas leader Khaled Mashal, in which he said he was "ready to cooperate with Fatah," was read at the opening of the congress on Tuesday.
Abbas and Mashal recently met in Qatar for the first time in two years.
On Tuesday, UN Secretary General Ban Ki-moon warned that hopes for a two-state solution were fading fast, decrying settlement building and home demolitions by Israel.
He also, however, criticized the Palestinians' "paralyzing lack of unity".