Abbas' spokesman Nabil Abu Redeineh told AP on Tuesday that there was pressure "around the clock from all sides in order to prevent us going to the General Assembly."
But he said the move toward statehood would not be reversed and adoption of the resolution would be "a major turning point in the Palestinian-Israeli track and ... a Palestinian and Arab achievement."
The Palestinians hope to use their upgraded status to join additional U.N. bodies, such as the International Criminal Court, where they could attempt to prosecute Israel for war crimes or crimes against humanity.
The draft resolution makes no mention of the ICC. U.N. diplomats said the issue was raised during discussions with the Palestinians by some governments. Israel reportedly wanted to include assurances that the Palestinians won't go to the ICC, and that the resolution does not infringe on sovereignty, but these amendments were rejected.
Mansour told reporters the Palestinians' top priority is resuming negotiations and not going to the ICC.
"I believe that the day after we adopt the resolution, if the other side is ready and willing to negotiate in good faith with us, I believe that the Palestinian leadership would reciprocate in a positive way," he said.
"I don't believe that we are going to be rushing the second day to join everything related to the United Nations, including to the ICC," Mansour said.
He said if Israel acts in good faith, according to international law, "I don't think that anybody will be going after them for anything."
But if Israel continues to violate the law, refuses to comply with U.N. resolutions and keeps building settlements, he said, the Palestinians will look at other options to bring them into compliance.
Following last year's move by the Palestinians to join the U.N. cultural agency UNESCO, the United States withheld funds from the organization, which amount to 22 percent of its budget. The U.S. also withheld money to the Palestinians, and the U.S. Congress has threatened similar sanctions if the Palestinians improve their status at the U.N. again.
Israel also retaliated by accelerating settlement construction and withholding funds from the Palestinian government.
Mansour said he is sure Abbas will try everything possible to avoid any punishment after the vote, but if "some negative things are going to be imposed on us we will deal with them in the best way that we know how."
He also expressed hope that the resolution will improve prospects for reconciliation between Hamas and Fatah.
Asked whether Hamas supports a two-state solution, which would imply recognition of Israel, Mansour said "I think they would — yes — because it is in the interest of the Palestinian people."
Associated Press Writers Josef Federman in Jerusalem, Karin Laub in Ramallah, Jamey Keaten in Paris and Bradley Klapper in Washington contributed to this report
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