Pakistan showed signs of heeding U.S. calls to robustly battle the Taliban as government troops, backed by helicopter gunships, clashed with militants near the Swat Valley and an official who brokered a peace deal with the insurgents was removed. The Obama administration has been talking with Pakistan's leadership in recent days to "encourage" its military not to cede more ground to the Taliban, according to senior U.S. officials. To support the effort and bolster stability in Pakistan, the State Department is seeking to accelerate delivery of $1 billion in aid, senior U.S. officials said. "Pakistan is in an emergency situation," Richard Holbrooke, the U.S. special representative for Pakistan and Afghanistan, said in an interview Sunday. "An argument could be made for the acceleration of the aid." Pakistani paramilitary maintain a position on a high post in the troubled area of Pakistan's Lower Dir district Sunday. Pakistan launched an operation against militants in a district covered by a government-backed peace deal. Islamabad's commitment to the truce in Swat was tested again Sunday when militants ambushed a convoy of paramilitary police in Lower Dir district, north of the Swat Valley. The army responded by shelling militant positions and strafing them from helicopters, said a senior military officer. One policeman and several militants were killed, Pakistan's military said. The paramilitary unit, the Frontier Corps, wrested at least one of the district's towns from Taliban control by late Sunday, Pakistan's military said. How much of the district remained under Taliban control was unclear. The Swat Valley has become a major militant base since the government struck a peace accord with the Taliban in mid-February. Militants have since advanced to surrounding districts. The government looked likely to abandon what has largely been its one-sided truce unless the Taliban completely pulled back to the valley, Pakistani officials and Western diplomats said. President Asif Ali Zardari's spokesman insisted Sunday the accord in Swat remained "intact," suggesting the military operation would be limited to Lower Dir. The accord saw the army pull back and the Taliban impose a harsh brand of Islamic law on Swat. The militants have also kept their weapons, which a Taliban spokesman said Sunday they needed to enforce the rulings of Islamic courts being set up under the peace deal. Taliban "do not lay down weapons," he said. Pakistan's military moved in to Lower Dir after the Taliban, who had come from Swat, reportedly began kidnapping prominent residents for ransom, a Pakistani official said. An indefinite curfew was imposed on the district, where 12 children were killed Saturday while playing with a bomb. The violence in Dir came after hundreds of Taliban fighters from Swat pulled out of the Buner district, south of the valley, which they seized last week. The government and Taliban officials said "local" Taliban remained in Buner -- 70 miles from Islamabad -- dug in at mountain camps and manning checkpoints in remote parts of the district. The Taliban have also sent scores of young men from Buner to training camps in Swat. The U.S. has pressed Pakistan to move against the militants, fearing they will build on gains in Swat to push further into the heavily populated heartland. Chairman of the Joint Chiefs of Staff Adm. Mike Mullen has talked with Pakistan's army chief, Gen. Ashfaq Kayani, in recent days, according to senior U.S. officials. Mr. Holbrooke is having regular discussions with Mr. Zardari, opposition leader Nawaz Sharif and Foreign Minister Shah Mahmood Qureshi. President Barack Obama has been leading the U.S. response, officials said. Mr. Zardari is due in Washington on May 6-7 for a meeting with Mr. Obama and Afghan President Hamid Karzai to be focused largely on better coordinating the fight against the Taliban. The meeting will also now focus on finding ways to quickly strengthen Islamabad's finances and fighting capabilities. Washington pledged $1 billion for Islamabad this month as part of a wider five-year $7.5 billion package, and that first installment can be distributed more quickly if Congress decides to do so. In another indication Islamabad may be having second thoughts about the truce, the top administrator for Swat and surrounding areas, Syed Mohammed Javed, was replaced over the weekend for allegedly maintaining close contact with wanted Taliban commanders -- although his local ties got him the job.Mr. Javed earlier this month met Faqir Mohammed, a Taliban commander whose forces have been battling Pakistani soldiers in the nearby Bajaur region. Intelligence officials in Islamabad say he has also met with al Qaeda's deputy leader, Ayman al-Zawahiri.Mr. Javed said he was being moved from Malakand as part of a "routine" transfer and denied having any contact with Mr. Zawahiri or other wanted militants. He said he hadn't been told his new assignment. Mr. Javed was named last year the commissioner of Malakand -- a region that includes Swat, Buner and Dir -- because of his close relationship with Sufi Mohammed, a radical cleric whose son-in-law leads the Taliban faction in Swat, say analysts. His replacement, Fazal Karim Khattack, now must contend with the Taliban and a peace deal that has begun to look increasingly one-sided.