American intelligence agencies have concluded that members of Pakistan’s powerful spy service helped plan the deadly July 7 bombing of India’s embassy in Kabul, Afghanistan, according to United States government officials.

The conclusion was based on intercepted communications between Pakistani intelligence officers and militants who carried out the attack, the officials said, providing the clearest evidence to date that Pakistani intelligence officers are actively undermining American efforts to combat militants in the region.

The American officials also said there was new information showing that members of the Pakistani intelligence service were increasingly providing militants with details about the American campaign against them, in some cases allowing militants to avoid American missile strikes in Pakistan’s tribal areas.

Concerns about the role played by Pakistani intelligence not only has strained relations between the United States and Pakistan, a longtime ally, but also has fanned tensions between Pakistan and its archrival, India. Within days of the bombings, Indian officials accused the Directorate of Inter-Services Intelligence, or ISI, of helping to orchestrate the attack in Kabul, which killed 54, including an Indian defense attaché.

This week, Pakistani troops clashed with Indian forces in the contested region of Kashmir, threatening to fray an uneasy cease-fire that has held since November 2003.

The New York Times reported this week that a top Central Intelligence Agency official traveled to Pakistan this month to confront senior Pakistani officials with information about support provided by members of the ISI to militant groups. It had not been known that American intelligence agencies concluded that elements of Pakistani intelligence provided direct support for the attack in Kabul.