Theresa May is to make an "unashamed" vow to ensure overseas aid spending benefits UK interests while also seeking to give private firms greater confidence to invest in Africa.
The Prime Minister will use a speech to outline her ambitions for the continent after arriving as part of a three-day trade mission to South Africa, Nigeria and Kenya.
Mrs May is expected to declare her desire for the UK to overtake the United States to become the G7's leading investor in Africa by 2022, amid warnings of "greater conflict and an increased susceptibility to extremism" emerging if jobs are not created.
Downing Street believes helping young people in Africa secure jobs will stabilise the economy of their country while also reducing the likelihood of them undertaking risky journeys to Europe.
The PM is also expected to reassert the UK's shift in strategy over aid spending - using the trip to encourage private sector investment alongside efforts to alleviate extreme poverty.
Britain's overseas aid budget totalled £13.9 billion in 2017, an increase of £555 million in 2016 and in line with the legal commitment to invest 0.7% of national income in this area.
It has proven a controversial pledge among some Tory backbenchers, with successive international development secretaries vowing to use the cash to help develop trade against the backdrop of Brexit.
Mrs May is expected to use her speech to outline investment in Britain's diplomatic network in Africa, with the use of trade experts to help encourage investment, amid growing influence on the continent from other countries including China.
Speaking at the First National Bank in Cape Town on Tuesday, Mrs May is expected to say the private sector is key to driving growth in labour markets and "unleashing the entrepreneurial spirit" in Africa.
She will say: "However, for a variety of reasons the private sector has not yet managed to deliver the level of job creation and investment that many African nations need.
"So I want to put our development budget and expertise at the centre of our partnership as part of an ambitious new approach - and use this to support the private sector to take root and grow."
Mrs May will add: "I am unashamed about the need to ensure that our aid programme works for the UK.
"So today I am committing that our development spending will not only combat extreme poverty, but at the same time tackle global challenges and support our own national interest. This will ensure that our investment in aid benefits us all, and is fully aligned with our wider national security priorities."
Mrs May will outline her ambition for the UK to be the G7's "number one investor in Africa" by 2022, adding Britain's private sector should invest the billions that will see "African economies growing by trillions".