Kofi Annan, fresh from a two-week tour of the region, told a news conference on Wednesday that most of the leaders he had spoken to felt the invasion of Iraq and its aftermath had been a "real disaster for them".
"They believe it has destabilised the region," he said.
However, Annan said that leaders in the region were split over whether the US-led force in Iraq should now pull out or stay.
"Many leaders think the US has to stay in Iraq until things improve, and that having created the problem they cannot walk away," he said.
Annan went on to explain the other school of thought: "Iran believes the presence of the US is a problem and that the US should leave. And if the US were to decide to leave, they would help them leave."
In Washington, Tony Snow, the White House spokesman, said he disagreed with Annan's characterisation of the situation.
"If you take a look at what's gone on in the region, you have attempts to establish democracies in Lebanon, you have an attempt to establish a democracy in the Palestinian areas, you have democracies now up and gaining their footing in Afghanistan and Iraq.
"And those are developments that are positive," Snow said.
Annan has angered Washington in the past by calling the Iraq-invasion "illegal" because it was launched without the approval of the UN Security Council, and by saying that the war had "not left the world a safer place".