"MEXICO CITY, Mexico (Reuters) -- Mexican billionaire Carlos Slim, the world's third-richest man, will give away a chunk of his fortune by matching donations to health, education and social programs in Mexico, a close aide said Wednesday.

Slim, who owns a telecoms and retail empire and has a fortune estimated at over $30 billion, will meet all contributions dollar for dollar, said Arturo Elias Ayub, his spokesman and aide.

""We want to offer Mexican or foreign foundations that we will match any amount they invest in social work in Mexico,"" Elias Ayub told Reuters.

It was unclear how much Slim's donations might ultimately total.

""The idea is social programs focused on real needs: education, health, nutrition, research,"" he said.

Slim is No. 3 on the Forbes list of the world's wealthiest people, behind Microsoft Corp. founder Bill Gates and investor Warren Buffett, who made his billions with insurance and investment company Berkshire Hathaway Inc.

Buffett recently signed over the bulk of his estimated $44 billion fortune to Gates' charitable foundation as part of a combined fight against disease and poverty around the world.

Slim has risen steadily on the Forbes list in recent years and now plans to join the group of major philanthropists.

Charitable foundations
He heads charitable foundations through two of his main companies, Telmex and Grupo Carso, which have combined endowments of over $3 billion.

Slim's Telmex foundation is funded with cash from the company operations while Carso's is mostly supported by personal donations from the businessman, his six children and other relatives.

Slim, 66, made the bulk of his fortune by turning former state-owned phone company Telmex into a cash cow in the mid-1990s.

The Telmex and Carso foundations have programs ranging from school scholarships to providing surgical equipment for hospitals.

Slim has in recent years become increasingly vocal about the need to create more jobs and improve education in Mexico.

He spearheaded an initiative in 2005 that called on politicians to reform Mexico's justice system, fight crime, boost public finances, improve health and education and develop infrastructure.

His public appearances to promote the initiative waned this year ahead of the July presidential election, which reopened a deep divide between Mexico's rich and poor
"