KABUL, Afghanistan — The closer integration of the feared Haqqani militant network into the leadership of the Taliban is changing the flow of the Afghan insurgency this year, with the Haqqanis’ senior leader increasingly calling the shots in the Taliban’s offensive, Afghan and American officials say.

The Haqqanis have refined a signature brand of urban terrorist attacks and cultivated a sophisticated international fund-raising network, factoring prominently in the United States military’s push to keep troops in Afghanistan. Just last month, the Haqqanis were believed to be behind a truck bomb attack in Kabul that killed 64 people and wounded hundreds.

Now, the group’s growing role in leading the entire insurgency has raised concerns about an even deadlier year of fighting ahead, as hopes of peace talks have collapsed. The shift is also raising tensions with the Pakistani military, which American and Afghan officials accuse of sheltering the Haqqanis as a proxy group.

Though it has always nominally been a branch of the Taliban, the Haqqani network was seen as largely autonomous. But the selection of Sirajuddin Haqqani, the group’s chief, to become the deputy leader of the Taliban during a leadership struggle last summer has turned out to be far from a symbolic move, officials say.