The official Iraqi news agency INA quoted a military spokesman in Baghdad as saying Washington has not reported the incident so that the pilot can escape or his body recovered by American forces if he has been killed.

The incident marked the worst escalation of the stand-off between Iraq and the US since the recent bombing of Iraq. The Iraqi spokesman said ground search had begun to locate the wreckage of the US aeroplane.

However, Pentagon only confirmed that Iraq fired surface-to-air missiles at two US planes North of the Iraqi city of Mosul yesterday and that the planes fired back, taking evasive action, and returned safely.

President Bill Clinton, meanwhile, said, ``Our pilots have theauthority to protect themselves if they are attacked.''

Iraq said four soldiers were killed when the US fighters hit the missile launch base. The US missile attacks led to the ``martyrdom of four of our valiant soldiers and the wounding of seven others,'' the spokesman said.

The US and British aeroplanes enforced a no-fly zone over the northern and southern part of the country to prevent Iraqi planes from targetting Kurds and Shiite Muslims living in the two regions respectively.

Iraq has said it no longer recognised the no-fly zones and warned it will fire at jets violating its air space.

Meanwhile, an Arab league summit called this week to discuss Iraq was postponed after sharp divisions among the Arab world came to the fore over the issue.

Arab league secretary general Esmat Abdel-Meguid said in Cairo the meeting of Arab foreign ministers to be held there tomorrow was postponed until January 24 on a request from some countries of the Gulf Cooperation Council (GCC).

However the United ArabEmirates, one of the prominent members of the six- member GCC, said it fully backed the Yemeni request for convening the summit and clarified it did not ask for any postponement, according to the official news agency, WAM.

WAM said the GCC foreign ministers are to meet in Riyadh today to consider ``the current situation in the Arab world, notably the holding of an Arab summit.''

Some reports in the press here indicated that Saudi Arabia had expressed reservations on an Arab summit fearing that it may call for lifting of United Nations sanctions againt Iraq.