The US has more than doubled its estimate of the number of people killed by terrorism last year.
The US missed several attacks from its original account
The state department said 625 people were killed in 2003, compared with the 307 it claimed in April.
The Bush administration seized on the original report as proof that its "war on terror" was succeeding.
US Secretary of State Colin Powell said there had been no attempt to deceive people, and blamed clerical and administrative errors.
A US official said the figure of 625 people killed worldwide was still lower than the previous year's 725 deaths.
2003: 208 attacks, 625 dead, 3,646 wounded
2002: 198 attacks, 725 dead, 2,013 wounded
Source: US state department
The first report had said both the number of attacks and those wounded by them had also fallen in 2003 compared with 2002.
The figures in its revised report, issued on Tuesday, refuted both those claims.
It said there were 208 acts of terror around the world in 2003 - not 190 as first stated. That was an increase on the 198 reported in 2002.
The number wounded leapt from 2,013 in 2002 to 3,646 last year. April's document had reported a fall to 1,593.
The US official said the government had originally failed to count a number of attacks in November and December 2003, including bombings in Turkey and Saudi Arabia.
The deaths of troops in Iraq were not counted as they did not qualify under the "terrorism" definition, which includes attacks on civilians and unarmed military personnel.
Despite the revisions to the Patterns of Global Terrorism report, the 208 attacks last year remained a marked fall from the 346 reported in 2001.
'Kerry trusted more'
Mr Powell said there had never been any attempt to bolster President Bush's cause by producing false information.
"The report is not designed to make our efforts look better or worse, or terrorism look better or worse, or to deceive the American people," he said.
The revisions came as a poll showed the US public becoming less sure that President Bush is the right man to lead the "war on terror".
An ABC News/Washington Post poll found 48% of respondents trusted Democratic presidential candidate John Kerry to do a better job of handling the campaign against terrorism, against 47% for Mr Bush.