Theresa May has said the commitment to spend 0.7% of national income on foreign aid will remain in the Tory manifesto.
The Prime Minister said the pledge "remains and will remain" if the Conservatives win the General Election on 8 June, although she stressed the need to make sure the money is spent "in the most effective way".
Mrs May said she was proud of the work the UK is doing overseas, such as helping to tackle the Ebola crisis in Africa and supporting Syrian refugees.
Her comments, on a campaign visit in her Maidenhead constituency, end speculation the party was preparing to drop the commitment from the Tory election manifesto.
Answering questions from reporters at a toothpaste factory, the PM said: "Let's be clear, the 0.7% commitment remains and will remain.
"What we need to do though is to look at how that money is spent and make sure that we are able to spend that money in the most effective way.
"I am very proud of the record that we have, of the children around the world who are being educated as a result of what the British Government, the British taxpayer is doing in terms of its international aid.
"The ability that we had to be able to help in the Ebola crisis, the work that we've been doing supporting Syrian refugees. I was in Jordan a couple of weeks ago in a school meeting some youngsters who are being given a good quality education. That's one of the things the United Kingdom is providing.
"So I'm very proud of the record that we have, we maintain that commitment but we have to make sure we're spending that money as effectively as possible."
Responding to the announcement, former chancellor George Osborne wrote on Twitter: "Recommitment to 0.7% aid target very welcome. Morally right, strengthens UK influence & was key to creating modern compassionate Conservatives."
There had been pressure from some Tories to drop the commitment, while on the other side there was lobbying from the likes of Save the Children, Unicef and Oxfam to keep it.
Mrs May was also asked whether older people could expect to see their pensions continue to rise, as they have done so far under the Conservatives since 2010.
But there was no commitment that she will keep the "triple lock" on pensions introduced by David Cameron, under which the state pension rises by the highest of inflation, average earnings or a minimum 2.5% each year.
Labour has pledged to keep the triple lock in place until 2025.
"What I would say to pensioners is just look what the Conservatives in government have done," Mrs May said.
"Pensioners today are £1,250 better off as a result of action that has been taken.
"We were very clear about the need to support people in their old age, and that's exactly what we've done."