Feinstein's visit was being seen as a follow-up to last week's trip to Islamabad by Special Envoy Marc Grossman, who was unable to break an impasse in Pakistan-US ties, largely due to Islamabad's insistence on an apology from Washington for a cross-border North Atlantic Treaty Organisation air strike that killed 24 Pakistani soldiers in November.
US officials had also signalled to their Pakistani interlocutors that Feinstein intended to take up the issue of Lashkar-e-Tayiba founder Hafiz Mohammad Saeed, for whom the US has offered a 10-million dollar bounty, during her planned meetings in Islamabad.
Following the cancellation of the visits by the US officials, Foreign Minister Khar's planned trip to the US and US Senate Foreign Relations Committee chairman John Kerry's visit to Pakistan have been ruled out any time soon, The News daily reported.
Questions have also been raised about Pakistan's participation in an upcoming NATO summit in Chicago that will hold crucial discussions on the endgame in Afghanistan.
The US has also held up reimbursements worth billions of dollars claimed by Pakistan for its expenses on the war on terror.
Pakistan's Ambassador to the US Sherry Rehman, who travelled to Islamabad to assist the government for the talks with Grossman, "failed in persuading officials concerned to follow a pragmatic approach in dealing with the US", The News reported.
The US and Pakistan have struggled to put their relationship on an even keel since the beginning of last year.
A string of crises -- including the gunning down of two men by Central Investigation Agency contractor in Lahore, the unilateral US military raid that killed bin Laden in the garrison town of Abbottabad and a cross-border NATO air strike -- took ties to a new low and affected counter-terrorism cooperation.
Following the air strike, Pakistan closed NATO supply routes to Afghanistan and forced US personnel to vacate Shamsi airbase, considered a hub for CIA-operated drones.
Pakistan Prime Minister Gilani ordered a parliamentary review of Pakistan-US ties, which culminated with a resolution passed by a joint session of parliament on April 12. The resolution asked the government to seek an unconditional apology for the NATO attack and demanded an end to drone strikes.
The US appears unwilling to end the drone attacks -- the latest missile strike was carried out shortly after Grossman's visit to Islamabad last week.
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