Kurdish leaders in Iraq have quietly expanded a request to Washington for sophisticated arms and protective equipment to battle the Islamic State, but American officials have so far rebuffed the appeals out of concerns about defying the Iraqi government, according to Kurdish officials.

The Obama administration’s reluctance to directly arm the Kurdish forces underscores the challenges the United States faces in Iraq, where it is seeking to expand its effort to help Iraqi forces combat militants without upsetting a fragile political balance between the country’s Sunnis, Shiites and Kurds.

A Kurdish official, speaking on the condition of anonymity to discuss official communications, said Kurdish leaders had presented the Pentagon with an expanded request for U.S. equipment, including mine-resistant armored vehicles and technology to counter improvised explosive devices, such as bomb-defusing robots. […]