The aid will focus on poverty reduction
Britain is substantially increasing its aid to Pakistan and outlining a new strategy for how it is spent.
International Development Minister Douglas Alexander is in Islamabad to announce that aid will double to £480m ($956m) over the next three years.
The move comes amid British security concerns over growing Islamic militancy in the country.
The increase will make Pakistan second only to India as the recipient of the UK's largest aid programme worldwide.
The BBC's Barbara Plett in Islamabad says the move appears to reflect - at least in part - London's concern about the influence of Islamic militancy on Britons of Pakistani origin and its impact on British troops fighting over the border in Afghanistan.
The aid - first agreed in 2006 - will continue to focus on poverty reduction and improving health care.
But there will also be an extra emphasis on the Federally Administered Tribal Areas (Fata) along the border, which serve as a base for militants linked to the Taleban and al-Qaeda.
And there will be a new emphasis on education.
Pakistan's education system is inadequate and underfunded, and has been accused of failing to counter a rigid form of Islam taught in some Islamic schools, or madrassas.
"We believe that strengthening the Fata secretariat contributes not solely to the security environment but just as significantly increases the capacity for development to be taken forward within that area," Mr Alexander told the BBC.
He said there were "a whole system of checks in place" to ensure the money was spent effectively.
"We have long experience of this working around the world, using systems here in Pakistan tried and tested from elsewhere. We're also significantly increasing money to civil society," he said.
There are no details about how the money will be used in the tribal belt.
Our correspondent says any British development programme there would be expected to face difficulties.
The tribal structures traditionally used to administer aid to the area have been weakened and discredited by the rise of the Islamist militants.
And the region is insecure for aid workers - especially those linked to the West - because the tribesmen see Nato and the United States as occupiers of neighbouring Afghanistan.
Such hostility has grown with increased US air strikes on suspected militants in the region.