THE United Nations is facing yet another challenge in Iraq, after the Security Council last week put the secretary-general in charge of selling Iraqi oil to finance the purchase of up to $1.6 billion worth of essential food and medical supplies. But Iraqi officials have signaled that they may reject the plan.The UN has no prior experience in dealing with the international oil market nor in administering the revenues of a member state. United States Ambassador Thomas Pickering says his government "recognizes that the [Security Council] resolution places a heavy burden on the secretary-general ... on a number of highly complex and technical issues never before tackled by the UN." The five permanent Council members - the US, Soviet Union, Britain, France, and China - have all promised to lend government experts to help the UN carry out its new tasks. UN officials and relief experts also say they are simply not in a position to feed indefinitely Iraq's 18 million people. They point out that previous massive operations in Africa and elsewhere have helped a maximum of 4 million people - and only for a limited period of time. There are 655 UN and international relief personnel currently inside Iraq, including 350 UN police. Iraq's ambassador to the UN, Abdul Amir al-Anbari, told the Council before the vote Thursday that the resolution was one of the most serious it had ever adopted. He accused the Council of trying to "starve the Iraqi people and blame it on the Iraqi government.... The authors actually want to hold the Iraqi people hostage and to place before it two options: either to allow colonial and neocolonial states to plunder its oil wealth and control it indefinitely, or to keep the state of starvation and life on the brink of disaster. "This will not be permitted by Iraq," he added. The Iraqis object most to the resolution's provision that the oil-sale revenues and food purchases be handled by the UN through an escrow account supervised by the secretary-general. The Iraqi ambassador suggested instead that the five permanent members buy Iraq's oil, and that Iraq order its supplies from the five big powers, so that they would have direct documentary evidence of Iraq's revenues and expenditures. Iraqi diplomats have also complained that oil contracts traditionally depend on the ability to guarantee supplies for at least a year, while the Council is only permitting sales within a six-month period. The Iraqis worry that in the current glutted oil market, they will not get a fair price - and that buyers will demand further rebates to compensate for the inconvenience of dealing with the UN's red tape. (But the US mission to the UN has reportedly been deluged with calls from interested American buyer s, presumably in search of bargains.) The Iraqi government will make its final evaluation after seeing more specific plans for the sale and the administration of the revenues, Ambassador al-Anbari told journalists after the Council session. Secretary-General Javier Perez de Cuellar has been asked to come back to the Council in 20 days with a plan for the sale of the oil and the purchase of food and medicine; it is expected to take shape after the UN chief meets in Geneva on August 25 with the heads of the various UN specialized agencies. Despite the unprecedented limitations the resolution puts on a member state's sovereignty, it met with virtually no opposition within the Council, and received the support of 13 out of 15 Council members. Almost all of them said they believed it was the only way to provide some relief to the hard-hit civilian population of Iraq. The vote was one more confirmation of the near-total lack of sympathy for Iraq. "It shows how badly they have played their cards in the postwar period," said one Iranian. Cuba was the only country to vote against the measure; Yemen abstained. Soviet deputy representative Valentin Lozinskiy said that Iraq's status had indeed been affected: "That is the meaning of enforcement actions under Chapter VII of the UN charter ... Iraq is obliged to perform certain measures by the Security Council, so necessarily its sovereignty is limited." In the Council session, Kuwait's UN Ambassador Muhammad Abulhasan called for a UN inquiry into Iraqi war crimes committed during its occupation of Kuwait, "when it oppressed the Kuwaiti people and wreaked destruction on the environment of the region." He later told journalists that Iraq's return of 3,216 gold bars had been completed Thursday. The Kuwaiti ambassador added that he expected stolen currencies, gold coins and bank notes to be turned over in the next few days, and museum objects the week after next.