Iraq has seen some increased violence since January, including suicide and car bombings, despite a sharp overall decline in attacks in the past eight months.
The Pentagon said last night the rise in violence was partly a result of recent US-led offensives against Islamist militants.
The US Defence Department's latest quarterly report on the war notes that in January 2008, high-profile attacks rose for the first time in five months.
Many of the comparisons in the report were given in percentages rather than figures.
There are now 162,000 US troops in Iraq, but the number is expected to fall to about 140,000 by the end of July.
General David Petraeus, the top US commander in Iraq, is widely expected to recommend a pause in the troop drawdowns when he testifies to Congress next month.
Meanwhile, the top US commander for the Iraq and Afghanistan wars is expected to resign after a magazine reported he was pushing President George W Bush to avoid war with Iran.
Admiral William 'Fox' Fallon is head of the US Central Command headquarters responsible for the Middle East.
He insisted he did not disagree with the Bush administration over Iran but perceptions of a rift made it difficult for him to do his job.
Defence Secretary Robert Gates dismissed suggestions that Admiral Fallon's departure made war with Iran more likely.
