WASHINGTON - The United States on Wednesday acknowledged 'challenges in relations with Pakistan after a report that Pakistan security agencies have arrested CIA informants who fed information to the US spy agency in the months leading upto the raid that led to the death of Osama bin Laden. But the Obama administration said that security cooperation with Pakistan remains in both countries best interests. The New York Times report about the arrest of CIA informants in the Osama bin Laden case spurred Congressional calls for closer scrutiny of US aid to Pakistan. In response, US spokesmen stressed the continued value of engagement with, and aid to, Pakistan, and said the Obama administration is committed to working through what they term challenges in the relationship. Administration spokesmen declined comment on the reported arrests. However at a Washington policy forum, Republican Senator Lindsey Graham said, without elaboration, that Pakistan had done 'more than arrest the informants, while lamenting leaks from a closed Senate intelligence briefing that apparently spurred the Times report. At the White House, spokesman Jay Carney said US relations with Pakistan are 'complicated, but that anti-terrorism cooperation with Pakistan is vital to American interests. State Department Deputy Spokesman Mark Toner said that the parade of high-level US visitors to Pakistan since the May 2 raid underlines the commitment of the two countries to 'work through their problems. 'I think weve been up-front about challenges in the relationship. But weve also been consistent in saying that Pakistan and the US need each other, he said. 'We need to work through these challenges, because its in both of our long term, and short term frankly, interests to do so, he added. There were bipartisan expressions of concern from US Congress members on Wednesday about the New York Times report and earlier accounts of leaks of US-provided intelligence by the Pakistani security apparatus that foiled raids on militant bomb factories along the Pakistani-Afghan border. Senator Graham called the intelligence incidents 'a dynamic that is undermining Congressional support for Pakistani aid, and which must stop. 'After Osama bin Laden, if youre listening in Pakistan, it is almost impossible for an American politician to continue to help Pakistan, he said. 'The American people are so sour on this relationship. And having said that, as hard as Ive been today on Pakistan, the worst thing we could do is abandon them. As long as theres some hope, I think we need to stay engaged, he added. At a Senate hearing, Democratic Senator Patrick Leahy asked witnesses including Defence Secretary Robert Gates and the military Joint Chiefs of Staff Chairman, Admiral Mike Mullen how long the US should go on supporting governments that 'lie to us. Mullen, among top US officials to visit Islamabad in recent weeks, said Congressional criticism of Pakistan is valid but said walking away from the relationship will only harm US interests. 'I dont push back on the challenge associated with it. Some of the criticism is more than warranted, he said. 'Nobodys worked that harder than me, very frankly, with the Pakistani leadership. And its a conscious decision I think that we have to make. And if we walk away from it, its my view itll be a much more dangerous place a decade from now, and well be back, he added. The New York Times said the CIA gave Pakistan low marks on counter-terrorism cooperation at last weeks closed Senate briefing. But a spokeswoman for CIA Director Leon Panetta said he had 'productive meetings last week in Islamabad on issues raised following the Osama bin Laden raid, and that the US-Pakistan partnership is crucial.