"I am losing people, and I am just not going to stand for that. I have been Pakistan's best friend. What does it say when I am at that point? What does it say about where we are?" Mullen told The Wall Street Journal in an interview.
Mullen who demits office by the end of this month said he was leaving with a muddled legacy on Pakistan, an area which he had made a top priority because its border region has been a haven for al-Qaeda and other militant groups intent on attacking US interest.
Explaining his switch, Mullen, said that the partnership approach with Islamabad, which he had long championed had fallen short and would be difficult to revive.
The Admiral took his conclusions to Congress last week where he declared publicly -- what until then had been confined to private remarks -- that Pakistan's military intelligence is collaborating with a militant group that US links for attack on Americans in Afghanistan, triggering a major rift between the two nations.
The shift by Mullen infuriated officials in Islamabad, who deny supporting militants, and cast a pall of uncertainty over the tenuous US-Pakistan bond, the daily reported.
Mullen during his tenure met Pakistan Army Chief Gen Ashfaq Pervez Kayani nearly 30 times and spoke with him countless time seeking Pakistan's support in the war against terrorism.
Mullen developed a bond with Kayani, amid roller-coaster relations between their countries, in which US officials periodically accused Pakistan of failing to crack down on militants, and Islamabad defended its efforts and its sacrifices, the daily reported.
The top US commander said he was disappointed when a major Pakistani offensive planned against Haqqani fighter in North Waziristan tribal area didn't happen.
The Admiral said he had worked out a plan with Kayani for a offensive this spring into North Waziristan that would have taken away a key haven from the Haqqani network.
Mullen had hoped to integrate US and Pakistani strategic, military and intelligence efforts, a goal that came to define America's role there, the Wall Street Journal said.
"Even now, though, he stressed that while Pakistan's Inter-Services Intelligence agency has provided strategic support to the Haqqanis, they don't necessarily control the details of the militant group's operations," the daily said.
"It is very clear they have supported them. I don't think the Haqqanis can be turned on and off like a light switch. But there are steps that could be taken to impact the Haqqanis over time," Mullen is quoted as saying.
The US commander's assessment is that the tattered relationship with Pakistan is at a low point and that the strategic partnership would now be harder sell in Washington.