Washington: In its bid to restore bilateral relations with Pakistan, US tipped off the country about two militant bomb making facilities in the restive tribal region but by the time the camps were raided, they were found empty.

US Defense Secretary Robert Gates said as an act of faith to restore relations with Pakistan, US intelligence in recent weeks shared the location of two such compounds in Pakistan's tribal areas. But by the time authorities reached the facilities, they had been vacated.

The Defense Secretary said the Obama administration was disappointed by the unexplained failure of a US effort to share intelligence with Pakistan.

The soon-to-retire Pentagon Chief said he was not certain how or why the effort went awry. He said "there was clearly disappointment on our part." Others have raised the possibility that Pakistan's intelligence service had tipped off the militants.

Gates said Washington is disappointed and suspicious that militants in Pakistan apparently were tipped off that American intelligence officials had discovered two of their suspected bomb-making facilities.

But he stopped short of concluding that Pakistani officials leaked the information to the al-Qaida-linked Haqqani insurgents. And Gates said such incidents must not derail US relations with Islamabad.

A little over two weeks before ending his 4 1/2-year tenure, Gates in the interview touched on a range of issues including his expectation of a smooth handoff to his designated successor, current CIA Director Leon Panetta. Gates will retire June 30; Panetta's Senate confirmation is expected shortly.

The Pakistan intelligence breach has only fueled unease in the US, where officials worry about links between the intelligence service there and some militant groups.

A US official said after telling Pakistani intelligence about the location of the two compounds, US drones and satellite feeds showed the militants clearing out the contents at both sites.

"We don't know the specifics of what happened," said Gates. "There are suspicions and there are questions, but I think there was clearly disappointment on our part."

Another US official, who spoke on condition of anonymity, said the assumption was that the Pakistanis had tipped off the Haqqanis.

Asked whether it was time to take a harder line with Pakistan, Gates counseled patience and noted that the Pakistanis have not forgotten that the US abandoned them in the late 1980s after the Soviets pulled out of Afghanistan.

"We need each other, and this relationship goes beyond Afghanistan," he said. "It has to do with regional stability, and I think we have to be realistic about Pakistani distrust ... and their deep belief that when we're done with al-Qaida that we'll be gone, again."
Despite recurring tensions between Washington and Islamabad, and questions by some in Congress about the wisdom of having spent billions of dollars on aiding Pakistan since the Sept 11, 2001, terror attacks, Gates said the effort has paid off.