The FEC on Monday provided The Associated Press with a spread sheet of potential overseas donors that did not include contributors who left their state designation blank. As a result, the list was incomplete.

The $3.3 million total does not include donors who have given less than $200 and whose contributions do not have to be itemized. Some of that money could also have come from overseas. About half of Obama's $455 million in contributions so far are unitemized. The campaign does not identify those donors.

Obama senior adviser David Axelrod, speaking to reporters en route to Nashville, Tenn., on Tuesday, noted that anyone can donate to the campaign through the Internet. "We monitor these things as best we can," he said.

Republican John McCain's campaign lists all his donors, even those who give less than $200, on his Web site.

The Obama campaign has begun to request passport numbers from donors to verify their citizenship.

Asked why the Obama campaign doesn't do the same and open its database to the public, Axelrod said the campaign returns improper contributions.

"Obviously we've got a huge database of contributors," he said. "It's valuable to our campaign... We're probably more forthcoming about disclosure than anyone."

Independent watchdog groups, however, have asked the campaign to provide more information about its fundraisers and to at least provide information about small donors by zip code or country from where they donate.