The US has offered its "deepest condolences" after up to 26 Pakistani soldiers were killed in cross-border Nato air strikes.

America stressed the "importance" of its ties with Pakistan following the deadly assault on a border checkpoint.
In a joint statement, US Secretary of Defence Leon Panetta and Secretary of State Hillary Clinton also backed Nato's intention to launch an immediate investigation.
Pakistan is reportedly set to review all diplomatic, military and intelligence links with the US and Nato following the incident.
A Nato spokesman has admitted it is "highly likely" its aircraft were behind the assault on Pakistani troops while hunting insurgents near the border.
The Pakistani government has responded by blocking the vital supply route for Nato troops fighting in Afghanistan.
It has also ordered the US to vacate a controversial airbase within 15 days, reports say.
The site, a remote desert outpost in southwest Pakistan, is reportedly used as a hub for covert CIA drone strikes. Pakistan previously told the US to leave it in June.
Protesters in Pakistan after a Nato airstrike allegedly killed military personnel at checkpoints
Pakistanis protest after news spread of Nato's alleged attack on its territory
Brigadier General Carsten Jacobson, spokesman for the Nato-led International Security Assistance Force (Isaf), said earlier: "Close air support was called in, in the development of the tactical situation, and it is what highly likely caused the Pakistan casualties.

"We are aware that there are Pakistani casualties, we don't know numbers, we don't know the magnitude of the incident."
Senior government official Mutahir Zeb said: "We have halted the supplies and some 40 tankers and trucks have been returned from the check post."
Pakistan's foreign office condemned the pre-dawn raid.
"Prime Minister Yusuf Raza Gilani has condemned in the strongest terms the Nato/Isaf attack on the Pakistani post," spokeswoman Tehmina Janjua said in a statement.
"On his direction, the matter is being taken (up) by the foreign ministry in the strongest terms with Nato and the US."
Pakistani officials said the attack happened at the Salala checkpoint, about 1.5 miles from the Afghan border, near where Pakistani troops are fighting Taliban militants.
"Nato helicopters carried out an unprovoked and indiscriminate firing... casualties have been reported and details are awaited," a military spokesman said.
The spokesman said the attack in the Baizai region of the Mohmand tribal area started at about 2am on Saturday. Convoys were then blocked at Jamrud town, west of Peshawar.
According to an official, helicopters attacked two outposts around 1,000ft apart from each other, one of them twice, and two officers were among the dead.
Nato convoy lorries blocked by Pakistan from crossing into Afghanistan
Pakistan shut the strategically important border crossing, halting Nato convoys
"The latest attack by Nato forces on our post will have serious repercussions, without any reasons," the senior Pakistani officer said.
Nato's spokesman Bgd Gen Jacobson was asked about the expected length of the convoy blockade and its effectiveness.
He told Sky News: "I will not speculate on how long this will last. For the time being, there is no problems on the Isaf side."
Convoys entering Afghanistan from Pakistan have become crucial to Nato operations, as Isaf learned last year when militants repeatedly attacked fuel tankers.
Saturday's attack is believed to have been the deadliest Nato strike on Pakistan soil during the 10-year war in Afghanistan. It is likely to destabilise already extremely tense US-Pakistani relations.
It is a little over a year since US helicopters accidentally killed two Pakistani soldiers near the Afghan border, whom the pilots mistook for insurgents.
Pakistan responded at that time by closing the Torkham border crossing to Nato supplies for 10 days until America apologised.
The latest deaths come just days after Pakistan forced its US envoy to resign.
Relations between the US and Pakistan have been especially strained following the killing of al Qaeda leader Osama bin Laden in May.
The unauthorised attack on the terror boss by US special forces inside the Pakistani military garrison town of Abbottabad caused widespread outrage across the troubled nation.
Pakistan called that raid a flagrant violation of its sovereignty.-sky news