The UK has agreed to give Uganda £700m in aid, the international development secretary has announced.
Gordon Brown says a world trade deal will signal stability
The money will be used to fight poverty in the country over the next 10 years, Douglas Alexander said.
He spoke from Uganda where he has been attending the Commonwealth heads of government meeting.
Earlier, Gordon Brown appealed in Uganda for a new global trade deal within weeks to promote stability in a period of financial turbulence.
He called for a fresh drive to inject urgency into the long-running current Doha round of global trade talks.
The Ugandan government has signed a Development Partnership Agreement which commits the UK to providing at least £70m each year.
It is a framework which says the Ugandan government must commit itself to respecting human rights and tackling corruption.
At least £15m will be used this year on projects in northern Uganda which has suffered from years of conflict.
On Saturday Mr Alexander visited a camp in the area for people displaced by the conflict.
Currently almost a third of the population of Uganda lives on less than $1 a day, but the situation in the country is improving, Mr Alexander said.
"Since 1992, poverty rates in Uganda have almost halved and between 1995 and 2005, the percentage of the population with HIV/ AIDS has fallen from 18.5% to 6.4%.
"By signing the Development Partnership Arrangement, the UK is showing its commitment to reducing poverty in Uganda even further."
Judith Melby, Christian Aid's Africa specialist, welcomed the investment, especially the £15m targeted for north Uganda.
"The war has ended and people who have spent 20 years in camps are finally going home to their villages and they really need the money. It is terrific, as long as it is used properly and the commitment to peace remains."
The prime minister was speaking in the Ugandan capital Kampala where he is attending the biennial Commonwealth heads of government meeting.
The leaders are holding private talks at their Lake Victoria retreat.
Mr Brown has already held talks with Indian Prime Minister Manmohan Singh during the three-day summit of the 53-nation Commonwealth in a bid to kickstart the process.
A new trade agreement is a fraught issue for the Commonwealth which comprises some of the world's richest and poorest countries.
The global talks have repeatedly stalled since their inception in Qatar's capital, Doha, in 2001.
Mr Brown said securing agreement would show the world that free trade and globalisation based on open markets, free trade and flexibility was "the best way forward to create growth and prosperity in the world economy".
"I think it's very important that in the next few weeks we push harder to get a trade agreement," he added.
"I think the importance for the world community is that, at a time of financial turbulence, we do everything in our power to show that we can bring about greater stability.
Mr Brown said cuts were needed in agricultural subsidies in European and American markets, along with progress in opening up manufacturing to international competition.
"We need to understand the sensitivities of rural farmers in India and elsewhere and at the same time I think there's a growing feeling that we should move to a conclusion to this round," he added.
The Indian premier said only that he agreed with Mr Brown who has also discussed a new trade deal with South African president Thabo Mbeki and Lesotho's premier Pakalitha Mosisili.
The first day of the summit was marred by violent clashes between protesters and police in Uganda's capital, Kampala, over alleged human rights abuses by Ugandan President Yoweri Museveni.
Pakistan has been suspended from the councils of the Commonwealth for civil rights violations under its emergency rule.