"We have to do something, I recognise the obligation," he said after testifying before the US senate on the White House's strategy towards Afghanistan and Pakistan.

More than 500,000 people have been displaced in recent fighting in the tribal regions of Pakistan, the UN refugee agency has said.

Aid package

In depth


 Q&A: The struggle for Swat
Talking to the Taliban
Pakistan's war
 Pakistan diary
 The fight for northwest Pakistan
 Riz Khan: Obama's 'AfPak' strategy
 Riz Khan: The battle for the soul of Pakistan
 Your views: Crisis in Swat

Holbrooke admitted that there had been indequacies in US strategy towards Pakistan and that there were similarities with the conflict in Vietnam.

"People ask me if this is another Vietnam and I would say quite frankly there are many similarities ... including, sometimes inadequacies in our own strategies," he told thr senate foreign relations committee. 

He urged the committee to pass a bill that would triple civilian aid to Pakistan to $7.5bn over the next five years.

It would put new emphasis on non-military aid with the aim of transforming Pakistani schools, clinics and roads in the tribal regions affected by the fighting.

"That's the only way that we have a prayer here," Holbrooke said.

US legislators have criticised the bill saying Pakistan must show greater accountability before the money is signed off.