Mansour said the meeting with UN chief Antonio Guterres "was not a pleasant experience for all of us," following the secretary-general's order to remove the report from the UN website and the resignation of senior UN official Rima Khalaf after she refused to withdraw it.
The report was swiftly condemned by US and Israeli officials, who reportedly called on the UN to reject it. Guterres' spokesman Stephane Dujarric said it had been published without any prior consultations and did not reflect his views.
Mansour said he and the ambassadors of Oman and Iraq delivered a message to Guterres during what he also called a "very frank but warm discussion about a painful subject to all of us."
"We care about the UN and the secretary-general, and we do not accept methods that are not in the culture of the United Nations," Mansour said. "You know by that what I mean; some people who are trying to inject bullying tactics and intimidation."
He stressed that "it is our collective responsibility to do everything we can to defend the UN and what it stands for."
Mansour wouldn't say who was doing the "bullying," telling reporters: "You know who I mean."
Khalaf, a UN undersecretary-general who headed the Beirut-based UN Economic and Social Commission for Western Asia, resigned Friday after refusing Guterres' request to take the report off its website.
Its authors concluded that "Israel has established an apartheid regime that systematically institutionalizes racial oppression and domination of the Palestinian people as a whole."
The resignation of Khalaf, a Jordanian, and the removal of the report were welcomed by Israel and the United States, Israel's closest ally.
US Ambassador Nikki Haley said in a statement: "When someone issues a false and defamatory report in the name of the UN, it is appropriate that the person resign. UN agencies must do a better job of eliminating false and biased work, and I applaud the secretary-general's decision to distance his good office from it."
But Palestinians praised the report's findings and expressed regret that it was taken off the website.
Palestinian President Mahmoud Abbas informed Khalaf by phone that she would receive the Palestine Medal of the Highest Honor in recognition of her "courage and support" for the Palestinian people, the official Palestinian news agency Wafa said Sunday.
Mansour said even though the report had been taken off the UN website "I think it is in the hands of maybe hundreds of thousands of people anyway" because of publicity about its withdrawal.
"Many people who were not even interested in the report are now interested and asking for copies, and it is provided to them," he said.