A former CIA official has accused the Bush administration of "cherry-picking" its intelligence on Iraq before the 2003 invasion.
Mr Pillar says warnings about the post-Saddam chaos were ignored
Paul Pillar writes in the Foreign Affairs journal that the White House used the intelligence to justify a decision it had already reached.
Mr Pillar was the national intelligence officer for the Near East and South Asia from 2000 to 2005.
The Bush administration has yet to respond to Mr Pillar's accusations.
The White House has previously denied claims that it manipulated intelligence to gather support for the war.
"Official intelligence on Iraqi weapons programmes was flawed, but even with its flaws, it was not what led to the war," Mr Pillar writes.
Instead, he says that the White House "went to war without requesting - and evidently without being influenced by - any strategic-level intelligence assessments on any aspect of Iraq".
"It has become clear that official intelligence analysis was not relied on in making even the most significant national security decisions, that intelligence was misused publicly to justify decisions already made, that damaging ill will developed between policymakers and intelligence officers, and that the intelligence community's own work was politicised," Mr Pillar writes.
He also blames the Bush administration for ignoring warnings that Iraq could easily fall into violence and chaos after the war to topple Saddam Hussein.
"In a deeply divided Iraqi society, with Sunnis resentful over the loss of their dominant position and Shia seeking power commensurate with their majority status, there was a significant chance that the groups would engage in violent conflict," Mr Pillar writes.
His comments come in a website preview of the March/April issue of Foreign Affairs, which is published by the Council of Foreign Relations.
The council is an independent US body aimed at improving understanding of foreign affairs.