Leaders of the world’s richest countries have capped a three-day summit in L’Aquila, Italy Friday, by discussing food security with their counterparts from African nations.

U.S. President Barak Obama and other Group of Eight leaders are expected to announce a $15 billion pledge over three years to help poor countries fight hunger and develop their own agricultural sectors.

Mr. Obama also held separate talks with South African officials.

The U.S. leader next meets with Pope Benedict in Vatican City Friday.  The White House says Mr. Obama and Pope Benedict will have “frank” talks on issues they disagree on, such as abortion, along issues on which they agree, such as helping the poor.

Earlier this week, the pontiff called for a new global economy driven by “people-centered ethics” and not just profit.

On Thursday, President Obama said the 17 industrialized and developing countries took important steps to prepare for a December meeting on climate change in Copenhagen.

The nations agreed on a goal for limiting global warming to just two degrees centigrade above pre-industrial levels, although they failed to agree on targets for reducing greenhouse gas emissions.

Also Thursday in L’Aquila, French President Nicolas Sarkozy warned Israel that any strike against Iran would be a catastrophe for the world.  A day earlier, the G8 said in a statement it is losing its patience with Iran’s refusal to abandon a suspected nuclear weapons program.

The group also condemned North Korea’s nuclear weapons program and missile testing.

The Group of Eight and leaders from Brazil, China, India, Mexico and South Africa also agreed to restart a Doha round of world trade talks by next year.

The G8 includes the United States, Japan, Germany, France, Britain, Italy, Canada and Russia.