The US military on Monday blamed the militant Haqqani network for a massive truck bombing attack against a NATO base in central Afghanistan that wounded more than 100.

Saturday's bombing killed two people, injured 77 US troops and about 25 Afghan nationals, US officers said.

"We believe the perpetrators of the attack were from the Haqqani network," Pentagon press secretary George Little told reporters.

"There's a very strong likelihood that top Haqqani leadership supported and were aware of the attack," Little added.

The network, which operates out of sanctuaries in Pakistan, has been blamed for some of the deadliest anti-US attacks in Afghanistan, including a suicide attack at a US base in the eastern province of Khost in 2009 that killed seven CIA operatives.

The network is closely allied to the Taliban and was founded by Jalaluddin Haqqani and is run by his son, Sirajuddin, both of them already designated "global terrorists" by Washington.

US officials have pressed Pakistan to crack down on the Haqqani militants in the northwest but remain frustrated as Islamabad has focused mainly on the Pakistani Taliban.

The group dates back to the 1980s when its leaders enjoyed friendly ties to the Central Intelligence Agency, as the US funneled money and arms to Afghans fighting Soviet forces.

The bombing reflected an organization with substantial resources and the ability to plan a serious attack, spokesman Captain John Kirby said.

"This was a large, large vehicle, with a large amount of explosives material. And you don't conduct that kind of attack without good resourcing, good planning and a fair level of coordination," Kirby said.

A spate of casualties made August the deadliest month yet for US forces in the war, and Kirby said fighting insurgents in central and eastern Afghanistan continued to be "tough."

Launched a month after the 9/11 attacks, the US-led military campaign under president George W. Bush, Operation Enduring Freedom, was intended to topple the Taliban and ensure Al-Qaeda could no longer use the country as a safe haven.

A decade of fighting in Afghanistan has since snowballed into a huge effort involving around 130,000 foreign troops from dozens of countries, with the resilient Taliban using homemade bombs in a bid to undermine the Afghan government and the NATO mission.