Among those opposed to the U.N. move, championed by Palestinian President Mahmoud Abbas, are Palestinian Prime Minister Salam Fayyad, former Prime Minister Ahmed Qureia and former Palestinian U.N. envoy Nasser al-Qudwa, the Israeli newspaper Haaretz reported.
Qudwa's opposition is particularly significant, Haaretz said, because he is considered the most experienced Palestinian official in dealing with the United Nations.
Qudwa, a nephew of late Palestine Liberation Organization Chairman Yasser Arafat, is also considered likely to run for Palestinian Authority president after Abbas retires, Haaretz said.
Abbas is determined to go through with the planned September move, which seeks international recognition the "State of Palestine" through a U.N. General Assembly vote. The recognition would be based on the Palestinian border that existed before the 1967 Arab-Israeli war.
The move also seeks to have Palestine then admitted as a full member of the United Nations.
"More and more senior Palestinians are beginning to reconsider the approach to the United Nations," a senior European diplomat who met with two Palestinian ministers told the newspaper.
An Israeli official who met with senior Palestinian leaders said, "Some of them are beginning to understand that approaching the United Nations might hurt Israel, but it won't help the Palestinians."
U.S. President Barack Obama expressed opposition to the Palestinian statehood effort May 19, saying, "Symbolic efforts to isolate Israel at the United Nations in September won't create an independent state."
The U.S. Congress passed a resolution six months ago opposing a unilateral declaration of Palestinian statehood in the United Nations.