Chad is one of the countries where aid could be targeted
The UK is to spend £1bn ($1.6bn) a year in overseas aid on countries that have recently emerged from conflict.
The money will target security and job creation rather than traditional areas such as health and education.
International Development Secretary Douglas Alexander is expected to unveil the move in a White Paper on Monday.
His department will also get a new look - branded UK Aid - to try to raise the profile of British government spending on international development.
BBC international development correspondent David Loyn says the government will double the amount it spends at the "harder end" of aid priorities.
This includes police, security and justice systems as well as funding to provide jobs as an alternative to war for ex-soldiers.
The aim is to try to prevent conflicts in 20 fragile states where about one third of the poorest people in the world live.
The change in emphasis is based on what are seen as success stories in Sierra Leone and Nepal which are both coming out of long and bitter conflicts.
Our correspondent says the challenge will be harder in places such as Democratic Republic of Congo, Sudan and Chad.
HAVE YOUR SAY
Aid should go to the hungry and those in need of treatment for ill health
David Endson, Stockport
But the view is that the goal of halving the number of people in the world living in poverty by 2015 will not be met without such a change, especially during the global economic downturn.
The Conservatives have announced their own plans for overseas aid.
They are said to include the possibility of "aid vouchers" to let people in poor countries shop around for the best schools and services.