The United States provided aid to Saddam Hussein even after Baghdad began building weapons of mass destruction during the Iran-Iraq war, a report said on Thursday.

Not only did the US fail to protest when it learned of Iraq's use of chemical weapons during the Iran war, it also kept supplying arms and intelligence to Baghdad during those years, The Washington Post reported on Thursday.

Private US laboratories supplied some strains of biological agents to Iraq. It was only after chemical agents were used against its own citizens did the US raise a voice of protest, it said.

The disclosure suggests that one factor that deterred the US from marching to Iraq in 1991 could have been the existence of these weapons.

Iraq hastily developed its chemical weapons programme in the 1980s when it found itself losing the war it had started against the revolutionary regime of Ayatollah Ruhollah Khomeini.

When Hussein seized Kuwait in 1990 and the first Bush administration put together a coalition to oust the Iraqis, there was great concern among the coalition forces that he would use the massive stocks of chemical weapons to protect his victory. But Hussein made different decisions.

In the current war, as in the last, the US has warned Iraq against the use of WMD while reserving the right to retaliate with "all the weapons" at its disposal.