The United Nations Secretary General Kofi Annan has rejected allegations of corruption in the UN-administered oil-for-food programme in Iraq.
Limited oil production was permitted during Saddam Hussein's rule
He described reports that UN officials had colluded in smuggling Iraqi oil through Turkey to evade sanctions as "outrageous and exaggerated".
"We had no mandate to stop oil smuggling," he told a news conference.
The now-defunct scheme was designed to help Iraq buy humanitarian goods and ease the impact of sanctions.
In his strongest attack so far against the claims, the UN chief asked how the UN could have prevented such trafficking with no presence in the northern Iraq.
"The US and the British had planes in the air. We were not there," he told reporters in New York.
"If you read their reports, it looks as if the Saddam regime had nothing to do with it. They did nothing wrong. It was all the UN."
Mr Annan also rejected conflict-of-interest charges involving his son, Kojo, who worked for the Swiss-based firm Cotecna.
In December 1998, the company was awarded a contract to monitor Iraqi imports under the oil-for-food program after a British firm withdrew because of US bombing.
"Neither he nor I had anything to do with the contracts for Cotecna," Mr Annan said.
"That was done in strict accordance with UN rules and financial regulations."
Launched in 1996, the oil-for-food programme was the largest humanitarian operation ever undertaken by the UN and was meant to help civilians.
Recent media reports have accused individuals and companies from more than 40 countries, including a senior UN official, of being involved in corruption and bribery in connection with the oil sales.
Mr Annan has approved an independent investigation into the allegations.
It is also being investigated by the General Accounting Office, an arm of the US Congress.
BBC UN correspondent Suzy Price says the allegations come at a sensitive time for the world body, which is involved in mapping out Iraq's political future.