WASHINGTON — Tensions between the American and Pakistani governments intensified sharply on Tuesday as senior Obama administration officials demanded answers to how Obama bin Laden managed to hide in Pakistan, and the Pakistani government issued a defiant statement calling the raid that killed the Al Qaeda leader “an unauthorized unilateral action.”

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John O. Brennan, the top White House counterterrorism adviser, said there were many questions about how the sprawling compound “was able to be there for so many years with Bin Laden resident there and it didn’t come to the attention of the local authorities.”

“We need to understand what sort of support network that Bin Laden might have had in place,” Mr. Brennan said during an interview with ABC on Tuesday.

The suspicions have intensified efforts by some members of Congress to scale back American aid to Pakistan, or cut it entirely, as lawmakers described Pakistan as a duplicitous ally undeserving of the billions of dollars it receives each year from Washington.

Still, Obama administration officials and some members of Congress seemed determined to avoid the kind of break in relations that would jeopardize the counterterrorism network the C.I.A. has carefully constructed over the last few years in Pakistan, and as the administration tries to end the war in Afghanistan, a conflict where Pakistan is a necessary, if difficult, partner.

On Monday, the Obama administration’s special envoy to Afghanistan and Pakistan landed in the Pakistani capital, Islamabad, and delivered what American officials described as a stern message to senior Pakistani military and intelligence leaders. The envoy, Marc Grossman, told them that patience in Congress was wearing thin, officials familiar with the discussions said.

Officials in Washington said they hoped to learn far more about the network that Bin Laden tapped for support by examining the trove of computer files and documents that members of the Navy Seals grabbed during Monday’s raid.

Top Pakistani officials have vehemently denied that Islamabad tried to harbor Bin Laden, and American officials said that at this point there was no hard evidence that any Pakistani officials visited the compound in Abbottabad, or had any direct contacts with Bin Laden.

Even as they pledged support for the United States’ deeply strained alliance with Pakistan, several top American officials said it was difficult to believe that Bin Laden could have spent years in a town populated by current and former Pakistani military officers — with a Pakistani military academy close by — without the complicity of some in the country’s government.

Senator Dianne Feinstein, the California Democrat who is chairwoman of the Senate Intelligence Committee, acknowledged that she had no evidence that Pakistan’s government knew where Bin Laden was hiding, but said the government had much to answer for.

“If they didn’t know, why didn’t they know? Why didn’t they pay more attention to it? Was it just benign indifference, or was it indifference with a motive,” she said.

A civilian official in the Pakistani government said he did not know if the Pakistani spy agency, the Directorate of Inter-Services Intelligence, helped Bin Laden hide or was simply unaware of his presence in Abbottabad. Either way, he said, the successful American raid was an international humiliation for the agency.

“I’m not denying the possibility,” the official said, referring to the ISI sheltering Bin Laden. “At worst, it’s that. At best, it’s total incompetence.”

He said he hoped the raid would lead Pakistanis — particularly military and ISI leaders — to recognize the deep credibility problem their county now faces internationally.

In his meetings in Islamabad, Mr. Grossman told Pakistani leaders they needed to take steps to stanch the tide of anger in Washington about Pakistan’s behavior, according to Obama administration officials familiar with the meetings.

In public, Mr. Grossman was more diplomatic, telling reporters in Islamabad on Tuesday that the United States was committed to its alliance with Pakistan and that Pakistan was “determined to curb terrorism.”

A senior Pakistani general on Tuesday repeated his government’s formal denials that the military or the ISI knew of Bin Laden’s location. Instead, he acknowledged a major intelligence lapse by the Pakistani police and security forces.

“To me, it’s a big embarrassment that the bastard was in this compound near the academy,” said the Pakistani officer, who spoke on condition of anonymity. “Clearly, the U.S. had better intelligence than we did about what was inside that compound.”

The general said Pakistan and the United States had cooperated in other counterterrorism operations in the Abbottabad area in recent weeks, notably a C.I.A. tip that led to Pakistan’s recent arrest of Umar Patek, one of the main Indonesian suspects in the 2002 Bali bombing.

The Pakistani government statement went further, saying that the ISI had “been sharing information with C.I.A. and other friendly intelligence agencies” about the Bin Laden compound since 2009.

Several American officials said they were puzzled about the statement, pointing out that the C.I.A. did not know about the compound until last August.

The raid has fueled anti-Pakistan sentiment in Congress, yet it is unclear — perhaps even unlikely — that there would be enough support to cut aid to Pakistan.

Speaker John A. Boehner, who just returned from a congressional visit to Pakistan and Afghanistan, said that any discussion about cutting aid or decreasing engagement with Pakistan in the aftermath of the Bin Laden strike was premature and that he would strongly oppose any such move.

“We both benefit from having a strong bilateral relationship, and I think we need to use this moment to strengthen the ties between our two countries,” Mr. Boehner told reporters. “This is not a time to back away from Pakistan.”

Senator Harry Reid, the Nevada Democrat and majority leader, also expressed reluctance about limiting aid to Pakistan, saying the country has been an anti-terror partner of the United States. “They’ve lost thousands and thousands of their soldiers fighting terrorists,” he said. “Now, this doesn’t mean we shouldn’t have more oversight, and I’m willing to do that.”

In Brussels on Tuesday, the national intelligence officer for South Asia, Neil H. Joeck, spoke about Pakistan at a closed meeting of ambassadors to NATO. According to people present for his presentation, which was based on a December 2010 National Intelligence Estimate on Pakistan, Mr. Joeck said American officials had little expectation that the Pakistani government would mount a serious campaign to wipe out Al Qaeda or Taliban safe havens in the most contested border areas of the country.

“He said there were simply too many ongoing suspicions of the U.S.,” said one foreign official.