A former top diplomat has said he felt "very uncomfortable" about the UK going to war in Iraq without UN backing.
Lord Jay, senior civil servant at the Foreign Office in the run-up to the 2003 invasion, said another UN resolution was "necessary".
But he told the Iraq inquiry that he did not "dissent" from the attorney general's advice to ministers at the time that the war was lawful.
The inquiry is considering the legal case for the Iraq invasion.
The UK and US abandoned efforts to get a UN resolution explicitly authorising military action in early 2003 in the face of opposition from France and Russia.
Critics of the war say this was needed to make the action lawful.
Lord Jay, permanent secretary at the Foreign Office between 2002 and 2006, said the resolution passed by the UN in November 2002 - giving Iraq a "final opportunity" to comply with disarmament obligations and warning of "serious consequences" if they did not, was "essential".
However, he said he believed it was "insufficient" to bring the international community behind military action.
"I felt very uncomfortable with the prospect of a conflict without UN Security Council resolution," he said.
"It seemed to me to take a step as important as going to war without the support of the international community was something I would have preferred not to have done."
But he stressed that his concerns were about building a political consensus behind action against Iraq and not about the legality of the war.
While he was aware that lawyers at the Foreign Office - some of who opposed the war - had "thoroughly debated" the legality of the conflict and many had "strongly held views", he said he was satisfied with the attorney general's judgement.
Lord Goldsmith told the inquiry earlier this year that he advised ministers that the invasion was lawful on the basis of Iraq's failure to comply with existing UN resolutions dating back to the end of the Gulf War.
"I had no reason to dissent from the judgement," Lord Jay said. "He was the government's legal adviser. It was for him to make that judgement."
A "clear statement" on the war's legality was essential to allow Foreign Office staff working in the region to support military activity, he added, since such a course of action would potentially put them in danger.
The legal case for going to war has been one of the key issues at the inquiry since public hearings began in November.
Senior Foreign Office lawyer Elizabeth Wilmshurst, who resigned in protest at the time, told the inquiry earlier this year that she believed the action was unlawful without further UN authorisation and described the UK government's consideration of the legal arguments as "lamentable".
Later on Wednesday, the committee will hear from Iain Macleod, the most senior legal adviser to the then UK representative to the United Nations, Sir Jeremy Greenstock.
Cathy Adams, a legal adviser to Lord Goldsmith between 2002 and 2005, will also give evidence.
Lack of intelligence
The inquiry, which is looking at the UK's role in the war and its aftermath, resumed hearings on Tuesday after being suspended for the general election.
Asked about the build-up to war, Lord Jay said he would not have "dealt with" President Bush in the way that former prime minister Tony Blair did.
While suggesting that Mr Blair may have offered President Bush "commitments, half given" over Iraq policy during 2002, he said he never believed the "game was over" in terms of the prime minister having made up his mind to support military action.
He also criticised what he said was a lack of "first-hand knowledge" about what was going on Iraq, saying the UK had had to rely on its allies in the region and intelligence for insight into what was going on in Baghdad.
"You really need need people on the ground feeding stuff back," he said. "If you don't have that, you are going to make mistakes."
The current session of hearings - which is set to include appearances by the former deputy prime minister John Prescott and former chief UN weapons inspector Hans Blix - will end on 30 July.
Inquiry chairman Sir John Chilcot has said he intends to publish a "reliable and authoritative" report around the end of the year.