Reports from the UN and Copenhagen say the outgoing head of the UN relief agency for Palestinians, Peter Hansen, is leaving his post against his will.
Peter Hansen has been the focus of Israeli criticism for a long time
Interviewed by a Danish newspaper, Mr Hansen said UN chief Kofi Annan had rejected his offer to stay on.
UN officials quoted by Reuters say this was due to a long campaign against him by Israel and the United States.
Mr Hansen said it was no secret that several members of the US Congress had petitioned for his departure.
Mr Hansen, a Dane, has lead Unrwa since 1996.
He has been critical of the Israeli army's conduct in the occupied territories, and Israel has repeatedly called for his resignation.
Mr Annan told reporters on Monday that Mr Hansen was among a number of UN officials who would be leaving their posts. He remains in the job until March when his mandate expires.
'US opposes reappointment'
Reuters reports UN officials as saying that the US, the single largest donor to the agency, has argued against the reappointment of Mr Hansen on grounds he had served long enough and the agency needed new blood, the officials said.
The US was the only member of the advisory board opposing Mr Hansen's reappointment, a UN official told Reuters.
Rocket or stretcher? Israel had to withdraw allegations against Unrwa
Mr Hansen has often clashed with Israeli officials.
He has criticised Israel over home demolitions, what he sees as indiscriminate fire by Israeli forces and Israeli policies that he believes contributed to economic collapse and growing hunger among about 1m refugees in Gaza.
In October 2004, Israel released a video tape it alleged showed militants transporting a rocket in an Unrwa ambulance. This proved to be false, and the Israeli army was forced to withdraw the allegation.
Mr Hansen accused the Israeli government of disseminating "deliberately inciteful, false and malicious propaganda".
Mr Hansen was also strongly criticised by Israel over comments he made to the Canadian Broadcasting Corporation in which he said his agency did not exclude Hamas members from working for it.
"Hamas as a political organization does not mean that every member is a militant and we do not do political vetting and exclude people from one persuasion as against another," Mr Hansen said.
Israel called for a UN investigation.
Unrwa was formed to relief the Palestinian refugee crisis that followed the establishment of Israel in 1948.
It currently provides regular food aid to about 1.5m Palestinians in the West Bank and Gaza Strip. It also runs schools and clinics, and provides shelter for thousands of Palestinians made homeless by Israel's house demolition policy.