US government officials told the newspaper that communications had been intercepted between Pakistani intelligence officers and militants who carried out the July 7 attack that killed 54 people.

The newspaper said it was the clearest evidence to date that Pakistani intelligence officers were actively undermining US efforts to combat militants in the region.

The unidentified US officials also said new information showed that members of Pakistan's Directorate for Inter-Services Intelligence, or ISI, were increasingly providing militants with details about the US campaign against them, allowing them to avoid missile strikes in Pakistan's tribal areas.

The ISI has maintained ties to militant groups in the tribal areas, in part, to contain Afghanistan's power, the The New York Times said.

It added that Pakistan's government had also become concerned about India's growing influence inside Afghanistan, including New Delhi's close ties to the government of President Hamid Karzai.

US officials believe the Indian Embassy attack was probably carried out by members of a network led by Maulavi Jalaluddin Haqqani, whose alliance with al Qaeda has allowed the militant network to rebuild in the tribal areas, The New York Times said.

The US officials cited gave the newspaper no specific details about the kind of support provided by the ISI officers, but said they were not renegades, indicating their actions might have been authorized by superiors.

"It confirmed some suspicions that I think were widely held," one State Department official with knowledge of Afghanistan issues said of the intercepted communications, according to The New York Times .

"It was sort of this 'aha' moment. There was a sense that there was finally direct proof."

The New York Times reported on Wednesday that a top CIA official travelled to Islamabad to confront senior Pakistani officials with evidence of ties between the ISI and militants operating in the tribal areas.