As American confidence in the Pakistani government wanes,the Obama administration is reaching out more directly than before to Nawaz Sharif,the chief rival of Asif Ali Zardari,the Pakistani president,administration officials said on Friday. American officials have long held Sharif at arms length because of his close ties to Islamists in Pakistan,but some Obama administration officials now say those ties could be useful in helping Zardaris Government confront the stiffening challenge by Taliban insurgents. The move reflects the heightened concern in the Obama administration about the survivability of the Zardari government. Gen David H Petraeus,the head of the United States Central Command,has said in private meetings in Washington that Pakistans government is increasingly vulnerable,according to administration officials. General Petraeus is among those expected to attend an all-day meeting with senior administration officials to discuss the next steps in Afghanistan and Pakistan,in advance of high-level sessions next week in Washington,when Zardari and President Hamid Karzai of Afghanistan will meet with Obama at the White House. Washington has a bad history of trying to engineer domestic Pakistani politics,and no one in the administration is trying to broker an actual power-sharing agreement between Zardari and Sharif,administration officials say. But they say that Secretary of State Hillary Rodham Clinton and Richard Holbrooke,the special representative for Afghanistan and Pakistan,have both urged Zardari and Sharif to look for ways to work together,seeking to capitalise on Sharifs appeal among the countrys Islamist groups. That could be a tall order,given the intense animosity between the men,not to mention the ambivalence that many American officials still have toward Sharif. Some Pakistani officials said that members of Zardaris Government already were reaching out to Sharif and that officials in Washington were exaggerating their influence over Pakistani politics. Obama administration officials have been up front in expressing dissatisfaction with the response shown by Zardaris Government to increasing attacks by Taliban fighters and insurgents with al-Qaeda in the countrys tribal areas,and along its western border with Afghanistan. During a news conference on Wednesday, Obama said he was gravely concerned about the stability of the Pakistani Government; on Friday,a Defence Department official described Zardari as very,very weak. The official said the administration wanted to broker an agreement not so much to buoy Zardari personally,but to accomplish what the administration believes Pakistan must do. The idea here is to tie Sharifs popularity to things we think need to be done,like dealing with the militancy, said the official,who insisted on anonymity to speak more candidly about American differences with Pakistans Government. Both Holbrooke and Clinton have spoken with Sharif by telephone in the past month,and have urged Zardaris increasingly unpopular Government to work closely with Sharif,administration officials said. We told them theyre facing a national challenge,and for that,you need bipartisanship, a senior administration official said. The Presidents popularity is in the low double digits. Nawaz Sharif is at 83 per cent. They need to band together against the militants.