The White House has refused to endorse a top U.S. military officer's accusation that Afghanistan's militant Haqqani network is acting as a “veritable arm” of Pakistan's main intelligence service.

White House spokesman Jay Carney said Wednesday that the comment made last week by departing Joint Chiefs of Staff Chairman Mike Mullen is “not language that I would use.”

Admiral Mullen made the accusation in congressional testimony last week. He said Haqqani militants blamed for attacks on U.S. targets in Afghanistan were acting with the support of Pakistan's Inter-Services Intelligence Agency, or ISI. Pakistan strongly rejects that charge.

Carney said the Obama administration believes there are “links” between the ISI and the Haqqani network, which enjoys “safe havens” in Pakistan. He said Washington wants wants Islamabad to take action against the network and its Pakistani safe havens.

Carney said the differences in the language used by the White House and Admiral Mullen are a “matter of semantics.” The White House spokesman also said Pakistan has been “very helpful” to the United States in the fight against the al-Qaida terrorist group “in particular.”

In an article published Wednesday, The Washington Post quoted unnamed U.S. officials as saying Admiral Mullen overstated the alleged role of the ISI in Haqqani attacks because there is a lack of clear evidence that the Pakistani intelligence agency directs or controls the militants.

In an interview with The Wall Street Journal published Wednesday, Admiral Mullen says he has been Pakistan's “best friend” but that he will not stand for losing U.S. military personnel in Afghanistan to Haqqani attacks. He says it is “very clear” that the Pakistani ISI has supported the Haqqanis, even though he does not believe the militants can be “turned on and off like a switch.”

Admiral Mullen will retire from his post this week.