US officials cautioned that the figure should not be seen as evidence that anti-occupation fighters are gaining ground because the effectiveness of their attacks declined and the Iraqis achieved numerous political milestones despite the ongoing violence.
Tim Keefe, a Marine Corps Major and a US military spokesman in Baghdad said "we are succeeding, and the Iraqis are succeeding".
But Daniel Goure, a defence analyst of the Lexington Institute think tank said, "It's a little hard on the face of it to claim we are being successful when the number of attacks increases by 30 percent.
"Given the fact that the total number of attacks are up and Iraqi casualties are rising, it is real hard to say we have seen any light in this tunnel," Goure added.
There were 34,131 attacks by fighters in 2005 compared with 26,496 in 2004, the US military said, counting all attacks regardless of their effectiveness against American and other coalition troops, Iraqi government security personnel and Iraqi civilians.
"Given the fact that the total number of attacks are up and Iraqi casualties are rising, it is real hard to say we have seen any light in this tunnel"
Daniel Goure, Defense analyst, Lexington Institute
The number of attacks involving improvised explosive devices (IEDs), or roadside bombs, increased to 10,593 in 2005 from 5607 in 2004, the military said. This figure includes IEDs found and eliminated by US forces before the anti-US fighters had a chance to detonate them.
Attacks using suicide vests rose to 67 in 2005 from seven in 2004, the military said. Suicide attacks with car bombs rose to 411 in 2005 from 133 in 2004.
"While you've seen a rise in the number of attacks, the effectiveness of those attacks has gone down," Keefe said, without providing exact numbers.
Keefe also said the number of attacks reflected US operations in western Iraq and elsewhere intended to take the fight to the anti-occupation groups.
"We're hunting them, forcing them either to flee or to fight. And when they fight, that's (counted as) an attack," Keefe said.
The Pentagon said there have been 2237 US military deaths in the war, which started in March 2003, with 1751 in combat and the rest in noncombat circumstances such as vehicle accidents, illness and suicide.
Another 16,472 US troops have been wounded in combat, the Pentagon said. IEDs are the top cause of death and injury for US troops in Iraq, often exploding under passing vehicle convoys.
The Pentagon said more than half of all US casualties stem from these homemade bombs, often buried along a roadside or hidden inside debris or even carcasses and usually detonated by remote control or with a timer.
Car bombings are on the rise
The number of US military deaths last year, 846, was nearly identical to the previous year, 848, while the number wounded in combat last year - 5939 - fell from 2004's total of 7989.
The United States now has 139,000 troops in Iraq, down from about 160,000 last month to help oversee the 15 December elections.