I am in Islamabad now, and attended an extraordinary press conference at the U.S. embassy with Sec. of State Hillary Clinton and the Chairman of the Joint Chiefs Mike Mullen.

They were here on an unannounced visit aimed at easing tensions between the two countries, in the wake of the U.S. raid that killed Osama bin Laden. Clinton, in an orange pants suit, looked exhausted and tense, and her words, aimed at a largely Pakistani press corps, were carefully chosen and delivered slowly.

Her whole pitch was an effort to move beyond Pakistan's anger, and embarrassment over America's decision to go it alone in killing bin Laden. She stressed that the U.S. had no evidence that top Pakistani officials knew he was living an hour from their capital, but hanging in the air was the reality of Pakistan's failure to find him.

Clearly Clinton and Mullen had delivered a tough message: your cooperation is vital in pursuing the violent extremists who still operate from your country; it is also crucial for both military and diplomatic efforts to end the fighting in Afghanistan.

The message was tempered by repeated praise for the Pakistani military's sacrifices in going after its own Taliban, but the two American officials made clear they also wanted more cooperation in going after Afghan Taliban.

One got the impression that the meetings between the U.S. officials and Pakistani counterparts had been much more frank than in the past. Such bluntness is long overdue. At least that way, it may become clear whether Pakistanis can be counted as allies.

But the difficulty of the task was underlined by Clinton's plea for Pakistan to understand that "anti-Americanism and conspiracy theories will not make its problems disappear." She was referring to the incredible distortions that fill the Pakistani press and the airwaves here – often in what seems to be an orchestrated campaign. They promote the wildest theories of how the United States aims to destroy their country.  Many Pakistani analysts believe their army and top intelligence agency, the ISI, feed such anti-American theories to the media.

Pakistanis have been quoting stories to me this week from the press  that claim a horrific terrorist attack on a Pakistani naval base last weekend was actually orchestrated by the United States, India and Israel – even though the Pakistani Taliban claimed credit.

A whole raft of stories making the rounds allege that Osama bin Laden was killed elsewhere and his body brought by the CIA to Abottabad to embarrass the Pakistani military. One variant of this tale claims that the killing took place in 2008 and the body was kept on ice for two years.

I could go on and on, but you get the point.

These theories can be heard from educated people, and – according to a Wikileaks document published in a credible Pakistani newspaper this week – are rife even in the top Pakistani military academy.  Many military officers are convinced, my Pakistani sources say, that America wants to seize their nuclear weapons.

Clinton said the United States must will try "to cut through …often deliberate misunderstandings, and conspiracy theories" that block cooperation.  The difficulty of that task was reflected in the exhaustion on her face.