CNN -- Headed into their first face-to-face debate, President Bush appears to be leading Democratic Sen. John Kerry among likely voters, with a clearer edge among registered voters.

The CNN/USA Today/Gallup poll shows that among likely voters, Bush was the choice of 52 percent, while Kerry was the choice of 44 percent and independent Ralph Nader garnered 3 percent. That result was within the poll's margin of error of plus or minus 4 percentage points.

In the broader category of registered voters, 53 percent supported Bush; 42 percent, Kerry; and 3 percent, Nader. That question had the same margin of error.

The poll was taken from Friday through Sunday, at the end of a week in which Kerry ratcheted up his criticism of Bush's Iraq policy.

On Thursday, the two men will debate in Miami, Florida, focusing on foreign affairs, during which Iraq is likely to be front and center.

Although the poll showed Americans divided almost evenly over whether they approve of the president's Iraq policy, 55 percent said it was not a mistake to send U.S. troops there, compared with 42 percent who thought it was a mistake.

And a majority, 53 percent, said they would support Bush if he wanted to send still more troops to Iraq.

Asked which man would better handle the situation in Iraq, 55 percent said Bush and 41 percent said Kerry. Two months ago, they were tied on that question.

The poll also showed Bush's job approval rating at 54 percent -- the highest since January -- and it found increased public approval for the president's handling of the economy, terrorism, the situation in Iraq and foreign affairs.

Among likely voters, 49 percent also said they believe Kerry would lead the country in the wrong direction, compared with just 44 percent who thought he would lead it in the right direction. But 54 percent of likely voters thought Bush would take America in the right direction; only 44 thought he would move the country in the wrong direction.

In the poll, Bush got higher marks than Kerry on handling the economy, Iraq and terrorism.

And asked which man would better handle relations with other countries, Bush -- charged by his critics with alienating the world community through unilateralism -- beat his Democratic challenger by a 52 percent to 44 percent margin.

Although half of those polled said the outcome of the election would have no effect on whether there is another terrorist attack in the United States, 31 percent said they think chances of an attack would be reduced if Bush were re-elected. Only 16 percent said they thought the chances of an attack would be reduced if Kerry was elected.

Kerry's military service in Vietnam -- which he showcased at the Democratic National Convention but has since come under attack by a group called Swift Boat Veterans for Truth -- has become less of an asset, the poll found.

In the latest poll, 19 percent of registered voters said Kerry's service made them more likely to vote for Kerry, down from 41 percent at the beginning of August, right after the Democratic convention.

The poll also found that the dispute over Kerry's antiwar activism after the Vietnam War is having more of a negative effect on his candidacy than questions about Bush's National Guard service are having on his electability.

A third of likely voters said Kerry's antiwar activity made them less likely to vote for him, compared with 49 percent who said it would have no effect. In contrast, 69 percent of likely voters said questions about Bush's Guard service would have no effect on their vote, compared with 23 percent who said it made them less likely to vote for the president.

This article was published by CNN.com.