World leaders open a summit Friday to formally approve an ambitious and costly 15-year blueprint to eradicate extreme poverty, combat climate change and address more than a dozen other major global issues.

Implementing the new development goals — expected to cost between $3.5 trillion and $5 trillion every year until 2030 — is expected to be the focus of the three-day summit that will include speeches by U.S. President Barack Obama, China's President Xi Jinping and the leaders of Egypt, India, Iran, Germany, Britain and France.

Kenya's U.N. Ambassador Macharia Kamau, one of the facilitators of negotiations, insisted in early August when the goals were agreed on by the U.N.'s 193 member states that the trillions needed are "not unattainable" because most money will come from domestic resources raised in countries, complemented by international development assistance.

But Microsoft co-founder and philanthropist Bill Gates said Thursday that "there's certainly no chance that that amount of money will be available next year," adding that "we'd be doing very well to have anywhere near that amount of money available by 2030."

Gates said, however, that if there is new innovation, for instance in nutrition by getting better seeds or a vaccine against tuberculosis, as well as economic growth, "we still think we can meet the goals, even though that specific number will be very, very hard to reach."

The document — called "Transforming our World: The 2030 Agenda for Sustainable Development" — which sets out the 17 broad goals and 169 specific targets, will be adopted after opening speeches at the summit.

Its overarching aims of reducing poverty and inequality and preserving the environment are expected to dovetail with an address to the General Assembly by Pope Francis immediately before the summit opens.

The 17 non-binding goals will succeed the eight Millennium Development Goals adopted by world leaders 15 years ago. Despite significant progress, however, the only one achieved before this year was halving the number of people living in extreme poverty, due primarily to economic growth in China.

Among the other new goals are ensuring "healthy lives," quality education for all, clean water, sanitation and reliable modern energy — and achieving gender equality, making cities safe, reducing inequality within and among countries, and promoting economic growth.