Foreign policy and national security concerns are considered more important by Americans this campaign year than at any time since the Vietnam War, and perceptions of success or failure in Iraq could be dominant in swaying swing voters in November, according to a new poll by the Pew Research Center for the People and the Press.

About 41 percent of those surveyed considered international issues such as the war in Iraq and terrorism the most important problems facing the country, while about 26 percent felt economic issues were most vital, according to the Pew survey, conducted in association with the Council on Foreign Relations.

"Barring a sizable shift in public opinion over the next few months, the 2004 election will be the first since the Vietnam era in which foreign affairs and national security issues are a higher priority than the economy," the Pew report concluded.

But like much of the electorate, swing voters -- those who are not committed to either candidate, including many in battleground states -- were split over which candidate is stronger on foreign policy and terrorism, the survey found. Swing voters tended to agree more with Democrats on foreign policy issues, but their opinions were closer to Republican positions on combating terrorism, pollsters said.

The survey included a number of danger signs for Bush, however, including among swing voters.

On Iraq, more than a month after the transfer of political power to an interim government, the survey found that about half of Americans surveyed -- 52 percent -- disapproved of the president's management of Iraq policy. Overall, 58 percent said the Bush administration did not have a "clear plan" for bringing Iraq to a "successful conclusion" -- a proportion that grew among swing voters, to 62 percent.

On eight of 11 foreign policy issues in the poll, "opinions of swing voters are closer to those of Kerry supporters than to those of Bush voters," the report said.

"Dissatisfaction with Iraq is shaping opinions about foreign policy as much, if not more than, Americans' continuing concerns over terrorism," the report concluded. "Continuing discontent with the way things are going in Iraq underlies public criticism of the Bush administration's overall approach to national security."

At the same time, Sen. John F. Kerry (D-Mass.) is not yet succeeding in convincing swing voters that he provides a viable alternative vision, the pollsters found.

"Iraq could be the tipping point," said Pew Director Andrew Kohut in an interview. "But even though things are bad in Iraq . . . Kerry hasn't made the sale on Iraq either. People are not more likely to say they have confidence in him than they have confidence in Bush, whom they disapprove of."

The poll was conducted among 2,009 adults from July 8 to 18, with an update on Iraq conducted Aug. 5 to 10 among 1,512 adults. The margin of error was plus or minus 2.5 percentage points for the entire survey and 3.5 percentage points for questions based on answers from one of the two survey periods.

The survey found a sharp increase in the number of Americans who expressed doubts about whether the Iraq campaign has helped the war on terrorism: 45 percent said it has helped, down from 62 percent in February.

About six in 10 Americans said Bush has been "too quick" in wielding military force, and a third said he made sufficient attempts to achieve diplomatic solutions, a proportion that has dropped by almost half since the onset of the Iraq war, the poll found. Kerry has focused on both issues in his criticism of Bush during the campaign.

Despite the tribulations of U.S. policy on Iraq, 54 percent said they favored staying in Iraq until the situation has stabilized. And six in 10 Americans supported Bush's controversial policy of preemptive strikes against perceived threats, even if the United States has not been targeted.

The survey found that 64 percent believed there were at least some circumstances in which torture is justified against suspected terrorists.

Kohut said that four in 10 people polled cited international and defense issues as most important was a striking departure from recent trends. In 1996, 5 percent of respondents in similar polls said they were basing their decisions on foreign policy or national security, a proportion that rose to 12 percent in 2000, he said.