John Kerry flies in to demand explanation of how Osama Bin Laden hid for so long

The US senator John Kerry will press Pakistani leaders for answers on Osama bin Laden in talks this week, but will be keen to ensure Pakistani anger over the raid does not subvert vital security co-operation.

The discovery of the al-Qa'ida leader living comfortably in a high-walled compound in Abbottabad virtually under the noses of military authorities has revived suspicion that Pakistani security agencies knew where he was all along.

Pakistan welcomed Bin Laden's killing as a big step against militancy. But the secret US raid to get him has been condemned as a violation of sovereignty which embarrassed and outraged the military. Military officials say it has caused a breakdown in trust and cast a shadow over security co-operation.

Pakistan might be tricky ally but it is vital to US efforts to combat Islamist militants and to efforts to stabilise Afghanistan, where US forces depend on Pakistani supply lines for water, food, fuel and other essentials.

In a sign of Pakistani anger, the chairman of Pakistan's joint chiefs of staff committee, General Khalid Shameem Wynne, cancelled a five-day visit to the US on Friday.

Details of Mr Kerry's visit to Pakistan have not been announced, but he will reportedly arrive in Islamabad for talks today.