Gordon Brown will hail a new $3bn drive to eradicate deaths from malaria in the developing world by 2015 at an emergency United Nations summit on world poverty and disease.
The initiative, to develop a vaccine and distribute bed nets and sprays over the coming years, is expected to save the lives of one million people who die from malaria every year.
It will be announced by the Prime Minister and Microsoft boss Bill Gates in New York, where 90 world leaders are gathering at the UN to discuss getting progress on the Millennium Development Goals back on track.
Mr Brown is also meeting Wall Street hedge fund chiefs to discuss the global financial turmoil which has sent shockwaves through the markets over the last week.
While the visit on Thursday will be dominated by meetings on the Millennium Development Goals, the premier is also using the New York trip to discuss the economic situation with other world leaders.
On Friday, he will take his call for greater transparency and supervisory systems in the financial sector to the UN general assembly, which has been meeting since Monday, in a setpiece address.
The Prime Minister arrived in the US on Wednesday evening with wife Sarah, who is also supporting the drive to redouble efforts on the Millennium Development Goals. She co-hosted a major dinner for influential women - including many first ladies - to raise awareness of the need to improve childbirth support in the third world.
The model Elle Macpherson and Sarah Ferguson, the Duchess of York travelled on the Prime Minister's flight from Manchester - where he left the Labour Party conference on Wednesday - in order to attend the dinner.
The action on malaria will be funded by a variety of public and private sector bodies, as well as a recently-announced $5bn commitment by the US.
The UK's support for research into malaria treatments and vaccines is to reach at least £5m a year by 2010. Britain is also prepared to provide £40m towards improving the availability of anti-malarial drugs. The summit will also see further commitments on education and healthcare.