The plan has not yet been approved, they said, but could bring an intelligence
windfall if they were allowed to launch cross-border attacks to capture
insurgents inside Pakistan.
Pakistani and Nato officials denied any such proposals were being considered.
However, the demands reflect the frustration of commanders on the ground,
whose soldiers are being killed by insurgents who can flee across the border
Analysts also suggested it was an attempt to put pressure on Pakistan,
America's awkward ally in the fight against al-Qaeda and the Taliban, to
make good on promises to launch a fresh military offensive.
American officials said they were particularly keen to capture - rather than
kill - militant leaders from the Taliban or the Haqqani network in order to
obtain intelligence about future operations.
"We've never been as close as we are now to getting the go-ahead to go
across," said a senior officer.
They also said an Afghan militia, backed by the CIA, had crossed into Pakistan
in pursuit of militants on at least two occasions since 2008.
Details of America's secret war in Pakistan - carried out with the support of
the government in Islamabad - have leaked out in recent weeks, with
diplomatic cables revealing how US special forces had fought alongside
Cross-border collaboration is desperately sensitive for the government of
Pakistan, which fears a violent backlash from Islamic hardliners if it is
seen to bow to American pressure.
Hussain Haqqani, Pakistan's ambassador to Washington, said the country's armed
forces were capable of tackling the threat from militants.
"We work with our allies, especially the US, and appreciate their
material support but will not accept foreign troops," he wrote on the
microblogging site Twitter.
The US has issued repeated requests for Pakistan to take on militant havens in
North Waziristan, from where fighters have launched attacks on international
troops in Afghanistan. The region is also home to terrorist training camps,
where recruits are believed to have plotted attacks on Europe.
However, Pakistan has so far refused to set a date for a military operation.
With Washington keen to start withdrawing some US troops from Afghanistan next
July, military and political leaders point to a renewed sense of urgency.
And last week, President Obama's war review identified tackling Pakistan's
havens as crucial to progress in Afghanistan.
Several analysts suggested the leak was designed to pressure Pakistan to take
tougher action before the US took matters into their own hands.
"This is a deliberate leak," said Ahmed Rashid, an expert on the
Afghan Taliban. "The Americans have been talking about this for the
last six months." Talat Masood, a retired Army general, said it would
be very difficult for Pakistan to allow US forces on to its soil despite
"They are coordinating, sharing intelligence on drone targets, but
allowing troops in would be crossing a red line," he said.
A spokesman for the Nato-led force in Afghanistan rubbished the idea, saying
it enjoyed a strong working relationship with Pakistan.
"This co-ordination recognises the sovereignty of Afghanistan and
Pakistan to pursue insurgents and terrorists operating in their respective
border areas," said Rear Admiral Gregory Smith.