ISLAMABAD: With Pak-US relationship at a crossroads, President Barack Obama’s trouble-shooter for Af-Pak region Senator John Kerry landed in Islamabad on Sunday with his toughest yet diplomatic assignment in Pakistan as Chairman of Senate Foreign Relations Committee; this time for assessing if Pakistan could continue to be an ally.

His visit comes at a time when the two countries are possibly facing the worst crisis in their relationship ever since they allied in the war on terror in 2001, which has compelled both sides to reassess the future of ties and parameters of cooperation.

So when Senator Kerry meets President Asif Ali Zardari, Prime Minister Yousuf Raza Gilani and other civil and military leaders, he would be asking some frank questions about how they perceive to carry on with the relationship.

According to a TV channel, Mr Kerry met Chief of the Army Staff Gen Ashfaq Parvez Kayani.

Before leaving the US for Pakistan, Senator Kerry had said he would press Pakistani leadership to demonstrate ‘real commitment to fight terrorism’.

That Mr Kerry hinted at “disturbing evidence” of Pakistani officials’ knowledge of terrorists’ sanctuaries in his pre-departure statement was in itself suggestive of the fact that the Obama administration was now readying to apply squeeze on Pakistan,notwithstanding some of the supportive statements that had come earlier, soon after Osama bin Laden’s killing in a US raid on May 2.

“Yes, there are insurgents coming across the border, yes they are operating out of North Waziristan and other areas of the sanctuaries, and yes, there is some evidence of Pakistan government knowledge of some of these activities in ways that isvery disturbing,” the influential Senator had said.

Analysts believe that Mr Kerry was the best choice available with President Obama to convey a firm message to Islamabad, which many think would be much similar to President George Bush’s “either you are with us or against us” soon after 9/11.

Mr Kerry is known as a friend of Pakistan in Washington and he isn’t brash even when delivering tough messages.

The calculated manner in which Senator Kerry set the tone for the visit indicates that unlike his previous visits to Islamabad, almost all of which came at crucial junctures, the messaging wouldn’t be all that subtle this time around.

Senior Fellow at Council on Foreign Relations Dr Daniel Markey, replying to a question from Dawn, cautioned that there could be very detrimental effects for the bilateral relationship if Mr Kerry, who lands in Islamabad as somebody supportive of partnership with Pakistan, were to return with a changed mind.

Dr Markey says the sense that Mr Kerry takes with him to Washington would depend on “How he is received. This would be very important. It is not just a matter of tactics or game playing or expressing frustration for political gains. It would have meaning to the relationship and perhaps in very significant ways.”

Dr Markey sees Pakistani politicians, military and intelligence joining together in US critique and fears that “pressure and politics can seize our leaders and force them to say and do things that seem tactically correct and potentially beneficial, but then are counter-productive”.

A joint sitting of parliament through a resolution after an in camera session on the Abbottabad US raid urged the “government to revisit and review its terms of engagement with the United States, with a view to ensuring that Pakistan’s national interests are fully respected and accommodated in pursuit of policies for countering terrorism and achieving reconciliation and peace in Afghanistan.”

Reuters adds: Senator Kerry will press Pakistani leaders for answers on Osama bin Laden but he will be keen to ensure Pakistani anger over the raid does not subvert vital security cooperation.

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

But officials in Pakistan’s civilian government said security cooperation with the United States would go on.

“There is difference of opinion but we’ll continue our cooperation with the world as well as the United States,” said one senior government official who declined to be identified.

The United States is likely to seek Pakistani help in an investigation into an imam of a Florida mosque and his two sons, arrested in the US on Saturday on charges of financing the Pakistani Taliban.

Three others charged were living in Pakistan, US officials said. Pakistan’s Foreign Ministry said it had yet to get a request for help but was ready to assist.

“As far as countering terrorism is concerned, there has been constant cooperation with the United States and there is no suspension of it,” said ministry spokeswoman Tehmina Janjua.

Mr Kerry told reporters in Afghanistan at the weekend that serious questions remained after the killing of Bin Laden.

The United States wanted Pakistan to be a “real” ally in combating militants, and while it needed to improve its efforts, the death of Bin Laden provided a critical chance to move forward, he said.

“We obviously want a Pakistan that is prepared to respect the interests of Afghanistan, and to be a real ally in our efforts to combat terrorism,” Mr Kerry told reporters in the northern Afghan city of Mazar-i-Sharif.

“We believe there are things that can be done better,” he said. “But we’re not trying to find a way to break the relationship apart, we’re trying to find a way to build it.”

The US administration has not accused Pakistan of complicity in hiding Bin Laden but has said he must have had some sort of support network, which it wants to uncover.

Mr Kerry said earlier it was “extraordinarily hard to believe” Bin Laden could have been in Pakistan for so long without any knowledge.