A Washington Post-ABC poll found that 56% of the public is willing to wait in order to win UN endorsement for war, with only 39% believing that the United States should "move quickly" without the security council's backing.
A poll by the non-partisan Pew research centre at the end of last week revealed a sharp increase in the number who believe the US does not yet have sufficient international support for war, up from 52% to 58%.
With the figure for those who back military action standing at above 60%, the polls do not suggest a huge growth in anti-war sentiment. Approval of US president George Bush's handling of the crisis remains high even though it has dropped six points to 55%, and his overall job approval ratings are down from 64% to 60%.
But on the crucial issues of how to proceed in the crisis most of the polls are edging slightly in his favour.
Only a minority (38%) believe that the US should push ahead with war without allies, but that figure has grown significantly since January when it stood at only 28%.
The US public remains even more sceptical about the performance of the UN, with 56% saying they disapproved of how the UN was handling the crisis. Those who believe that Mr Bush has explained clearly why the US might use military force has grown from 42% to 53% and an even larger number think that the US secretary of state, Colin Powell (61%) has explained clearly what is at stake.
While most would prefer a war to be supported by the United Nations, most (57%) would also support an attack without it, if America was flanked by key allies such as Britain, Australia and Italy, according to the Washington Post. Three-quarters believe that war is inevitable.
Overall, while polls show a considerably higher proportion opposed to war than usual at such times it remains a minority and past evidence suggests that support for military action hardens considerably once war starts.
According to Peter Feaver of Duke University, co-author of a forthcoming book on public opinion and war, since the Korean war 10% of Americans have opposed all military action who can never be won over and one third support all wars. Of the remaining 50%, around half are "casualty-phobic". One Pew poll suggests the prospect of mass casualties drives support down sharply.
So if the polls indicate backing for war, that support is qualified on there being international support for an attack and on all other options being exhausted - a crucial factor as the security council moves into its diplomatic endgame.
Those who would like to see a second UN resolution remains steady at 57%. Those who believe that there has been a direct link between Saddam Hussein and the terrorist attacks of September 11 has fallen (from 66% to 57%) along with the number who think the inspectors have proof that Iraq is hiding weapons of mass destruction.
Only a third believe the US is winning the war against terrorism, and less than half feel that Mr Bush has a coherent plan for dealing with terrorism.
They also show sharp differences both in race and gender. Women are far less likely to support war than men (63% to 73%) while only 44% of African-Americans support a war, compared with 73% of whites and 67% of Hispanics.
