BAGHDAD, August 26, 2009 (AFP) - The massive truck bombings that struck Baghdad last week show that insurgents are adapting their tactics and changing targets to try to destabilise the government, the US military said on Wednesday.

But Brigadier General Steve Lanza, a US army spokesman in Baghdad, told reporters that the bombers failed to achieve their goal.

"What they are looking to do is attack the government," Lanza said of the devastating attacks against the ministries of finance and foreign affairs that killed 95 people and wounded about 600 others.

"Why? Perhaps to fracture national unity... perhaps to (make) the population lose trust and confidence in the government... so that the blame game starts, which could lead to a breakdown in the security forces, which possibly leads to militias being formed," he added.

Lanza also said the attacks had not sparked a flare-up of sectarian tension or revenge attacks.

"We knew this was coming but it has not accomplished its purpose... to foment sectarian violence, and we have not seen the national government collapse.

"We didn't have the 100 people (killed) that we had when I was here a couple of years ago, when you wake up in the morning and there were bodies on the street in terms of retribution," he said.

"We have seen the national government, in their way, grasp their sovereignty and continue to move forward."

On Sunday, Iraq aired a video showing a former police chief confessing to last Wednesday's bombing at the finance ministry, which came minutes before a similar attack at the ministry of foreign affairs.

But an Al-Qaeda-linked group called the Islamic State of Iraq also claimed responsibility for the truck bombings.

Lanza said Al-Qaeda in Iraq now consisted of three strands -- opportunists, nationalists and hard-core believers -- and that although there will be "bumps along the way" the country was still making progress.

"The Japanese and the Koreans are still here wanting to invest," he said.

"We're bringing the Japanese to Basra for an investment conference. I acknowledge the attacks but I do not acknowledge that the government is moving backwards. This is different from the past."

Lanza also denied that a recent surge in bombings was a consequence of the withdrawal of US combat troops from urban centres across Iraq on June 30.

"When the Americans were here there were still attacks on the population," he said. "The time of transition on June 30 was the right time to do this."