Palestinian Authority President Mahmoud Abbas is expected to ask the UN to upgrade the Palestinians’ status to “non-member observer state”.
Israeli PM Benjamin Netanyahu will set down a “clear red line” over Iran’s nuclear programme, officials say.
Israel and the West suspect Tehran is trying to build nuclear weapons, while Iran insists its programme is peaceful.
On Wednesday, Iranian President Mahmoud Ahmadinejad accused Western countries of nuclear “intimidation”, in a UN speech boycotted by the US and Israel.
“Continued threat by the uncivilised Zionists [Israel] to resort to military action is a clear example of this bitter reality,” he told the General Assembly.
Later UK Prime Minister David Cameron told the 193-nation gathering: “Iran will continue to face the full force of sanctions and scrutiny from this United Nations until it gives up its ambitions to spread a nuclear shadow across the world.”
In his address to the General Assembly on Tuesday, US President Barack Obama stressed the US would “do what we must” to stop Tehran acquiring nuclear arms.
On Thursday, an Israeli official told reporters that Mr Netanyahu would “set a clear red line” which, if crossed, would lead to military intervention against Iran.
“Israel and the US have a common goal to prevent Iran from obtaining nuclear weapons. The prime minister’s remarks drawing a red line will help that this is attained,” the Associated Press news agency quoted the official as saying.
Mr Netanyahu recently warned that Iran was only six or seven months from having “90%” of what it needed to make a nuclear bomb and that it needed to be stopped.
In his own speech, Mr Abbas is expected request “non-member observer state” status for the Palestinians by the end of 2012.
Last year, a bid for full-member status failed because of a lack of support in the UN Security Council.
Currently, the Palestine Liberation Organisation only has “permanent observer” status.
The change would allow Palestinians to participate in General Assembly debates. It would also improve their chances of joining UN agencies and the International Criminal Court.