Poll results pose dilemma for Obama administration as it tries to bolster support for continued presence in Iraq and Afghanistan

One in three US veterans of the post-9/11 military believes the wars in Iraq and Afghanistan were not worth fighting, and a majority think that, after 10 years of combat, America should be focusing less on foreign affairs and more on domestic problems, according to an opinion poll.

The findings pose a dilemma for the Obama administration and Congress as they struggle to reduce the huge budget deficit and reconsider defence priorities while trying to bolster public support for the continued presence in Iraq and Afghanistan.

Nearly 4,500 US troops have been killed in Iraq and some 1,700 in Afghanistan. Combined war costs since the September 11 terrorist attacks have exceeded $1 trillion.

The results of the survey, presented by the Washington-based Pew research centre on Wednesday, portray the war veterans as proud of their work, scarred by warfare and convinced that the American public has little understanding of the problems that wartime service has created for military members and their families.

They were more likely than other Americans to call themselves Republicans, and to disapprove of Barack Obama's performance as commander in chief. They also were more likely than previous generations of veterans to have no religious affiliation.

Pew, a nonpartisan organisation that studies attitudes and trends, called the study the first of its kind. The results were based on two surveys conducted between late July and mid-September. One polled 1,853 veterans, including 712 who had served in the military after 9/11 but were no longer on active duty. Of the 712, 336 had served in Iraq or Afghanistan. The other survey questioned 2,003 adults who had not served in the military.

Nearly half of post 9/11 veterans said deployments had strained their relationship with their spouses and a similar number reported problems with their children. However, some 60% said they and their families benefited financially from having served in a combat zone. Asked for a single word to describe their experiences, the veterans suggested: "rewarding", "nightmare", "eye opening" and "lousy".

There are about 98,000 US troops in Afghanistan, where the conflict began with a US-led invasion on 7 October 2001. Obama's 2008 presidential campaign centred on a pledge to withdraw from Iraq and strengthen the military campaign in Afghanistan. He is on track to have US troops out of Iraq by the end of this year, and in July he announced that he would pull 10,000 troops out of Afghanistan this year and 23,000 more by next September.

The Pew survey found that veterans were ambivalent about the net value of the wars, although they were generally positive about Afghanistan, which has been a more protracted but less deadly conflict for US forces.

One in three veterans said neither war was worth the sacrifice; a view shared by 45% of the public polled. Some 50% of veterans said the campaign in Afghanistan had been worthwhile; 41% of civilians agreed. Among veterans, 44% said the war in Iraq was necessary; 36% of civilians shared that view.

Of the former service members who were seriously wounded or knew someone who was killed or seriously wounded, 48% said the war in Iraq was worth fighting, compared with 36% of those with no personal exposure to casualties.

Exposure to casualties had an even larger impact on attitudes toward the war in Afghanistan. Some 55% of those exposed to casualties said the military campaign in Afghanistan had been worth the cost to the US, whereas 40% of those who were not exposed to casualties held that view.

Pew said its survey results found "isolationist inclinations" among the war veterans. About six in 10 said the US should pay less attention to problems overseas and instead concentrate on issues at home. In a survey it conducted earlier this year, a similar share of the public agreed.

The results also reflected what many view as a troublesome cultural gap between the military and the public. Although numerous polls have shown that Americans hold troops in high regard, the respondents in the Pew research admitted to a lack of understanding of what military life entails. Only 27% of adult civilians said the public understood the problems facing those in uniform, while the proportion of veterans who said so was even lower at 21%.