Evidence of such weapons has not been found and a growing number of arms inspectors have criticised pre-war intelligence claims, but 54% of respondents still believed Iraq had the weapons.
On 9 July this year, the Senate Intelligence Committee issued a blistering report on the investigation into pre-war claims of Iraq’s capacity to wage war against its neighbours and develop WMDs.
The report stated that the intelligence used to justify the war was inaccurate, unsubstantiated, unwarranted, out-of-date, negligently analysed and misrepresented, thereby exhibiting "a broken corporate culture and poor management".
Linked to al-Qaida?
Despite the report, the poll indicated that 35% of respondents believed Iraq was either closely linked with al-Qaida before the war and 15% thought it was directly involved in the September 11 attacks on the US.
The poll which was released on Friday by the programme on international policy attitudes at the University of Maryland found the numbers on both questions had dropped in the face of evidence that both pre-war claims might have been false.
President George Bush consistently equates the "war on terrorism" with the war in Iraq, but has now replaced his claims that Iraq had WMDs with claims that Iraq had the "capability" of building such weapons.
Worsening US image
Seven in 10 in the poll said they believed the US went to war in Iraq based on false assumptions. A similar number said the war in Iraq had worsened America's image in the world.
A majority, 55%, said they did not think the war in Iraq would result in greater peace and stability in the Middle East.
In various polls, people have been evenly split on whether the war in Iraq was the right or wrong thing to do - a sharp drop from a few months ago for those who had thought it was right.
The poll of 733 adults was conducted by Knowledge Networks from 5-11 August and has a 3.5% margin of sampling error.