Acknowledging that trust deficit existed between the United States and Pakistan, America's top military general on Monday said it would take a long time for both countries to bridge that gap.

"We have a long history of support for Pakistan. And we've also left them hanging several times. So, it's going to take, I think, a long time to fill up that trust gap," Admiral Mike Mullen [Images], chairman of Joint Chiefs of Staff told CNN.

"That's one of the reasons that I go there so often to understand really through their eyes, what their challenges are and try to rebuild that trust," Mullen, who has visited Pakistan as many as 14 times in the recent past, said.

Mullen, who was the first top US official to publicly say that the leadership of the Afghan Taliban [Images] is concentrated entirely in Pakistan, said he has seen a substantial change in the country's attitude towards the Taliban and Al Qaeda [Images].

"I would say it is shifting," he said, asked if there was any change in Pakistan's attitude towards militants.

Mullen said lately there has been a lot of focus against militancy, commending Pakistan Army [Images] Chief Ashfaq Parvez Kayani [Images] for conducting the 'challenging' military operations.

"These are discussions I've had with General Kayani... And I've met with him many, many times," he said. "I see more and more focus on this... He just finished his ninth campaign over the last year, year-and-a-half, up in South Waziristan -- very challenging for him. He's shifted his forces over there, learning counterinsurgency," Mullen said.

The situation in the troubled Swat, he said, was 'completely reversed,' as against a year ago.