The Pentagon and CIA are stepping up America's secret war against the Taliban and al-Qaeda in Pakistan by secretly diverting aerial drones and missiles from Afghanistan.
Predator and Reaper drones have been lent by the US military to the CIA as part of a shift in strategy that underlines the Obama administration's view that Pakistan is unable or unwilling to target Islamist sanctuaries on its own soil.
Tensions between the US and Pakistan have flared after a key route used to supply American troops in Afghanistan was shut after three Pakistani soldiers were killed in an attack by a Nato helicopter gunship.
On Friday, insurgents attacked fuel tankers in Pakistan in another indication of the increasing vulnerability of Western supply routes.
The additional drones enabled the CIA to increase the number of strikes in Pakistan in September, averaging five strikes a week that month, up from an average of two to three per week.
This increase in drone activity was partly aimed at disrupting a suspected terrorist plot to strike in Western Europe. Americans officials believe Osama bin Laden and other al-Qaeda leaders are behind plots potentially aimed at Britain, France and Germany.
American surveillance drones are flown over Pakistan and intelligence gained passed to Islamabad. But Pakistan has formally banned US military operations on its soil, citing the country's sovereignty.
But the CIA has secretly conducted missile strikes launched from drones with Pakistani complicity. This has allowed Pakistan to condemn the strikes, which are strongly opposed by its predominantly anti-American population.
"You have to deal with the sanctuaries," said John Kerry, chairman of the Senate Foreign Relations Committee Chairman, told the Wall Street Journal. "I've pushed very, very hard with the Pakistanis regarding that." Mr Kerry discussed the issue with Shah Mehmood Qureshi, Pakistan's foreign minister, in Washington last week.
The secret arrangement between the Pentagon and CIA underlines the consensus in the Obama administration that safe havens on Pakistani territory near the Afghan border is the major obstacle to success in the war in Afghanistan.
"When it comes to drones, there's no mission more important right now than hitting targets in the tribal areas, and that's where additional equipment's gone," an American official told the Wall Street Journal.
"It's not the only answer, but it's critical to both homeland security and force protection in Afghanistan."
The proposal for the CIA to use military resources emerged during last year's Afghanistan-Pakistan policy review. There was resistance from some at the Pentagon who argued that the drones were needed against the Taliban in Afghanistan.
Since taking command in Afghanistan in July, Gen. Petraeus has placed greater focus on the tribal areas of Pakistan, according to military and other government officials.