* African leaders meet to discuss key details of free-trade bloc

* Potential for Africa's $3.4 trillion economy is massive

* Hurdles remain, such as corruption and poor infrastructure

By Boureima Balima

NIAMEY, July 7 (Reuters) - African leaders met on Sunday to launch a continental free-trade zone that if successful would unite 1.3 billion people, create a $3.4 trillion economic bloc and usher in a new era of development.

After four years of talks, an agreement to form a 55-nation trade bloc was reached in March, paving the way for Sunday's African Union summit in Niger where attendees will unveil which nation will host the trade zone's headquarters, when trading will start and discuss how exactly it will work.

It is hoped that the African Continental Free Trade Area (AfCFTA) - the largest since the creation of the World Trade Organization in 1994 - will help unlock Africa's long-stymied economic potential by boosting intra-regional trade, strengthening supply chains and spreading expertise.

"The eyes of the world are turned to Africa," Egyptian President and African Union Chairman Abdel Fattah al-Sisi said at the summit's opening ceremony.

AfCFTA "will reinforce our negotiating position on the international stage. It will represent an important step."

Africa has much catching up to do: its intra-regional trade accounted for just 17% of exports in 2017 versus 59% in Asia and 69% in Europe, and Africa has missed out on the economic booms that other trade blocs have experienced in recent decades.

Economists say significant challenges remain, including poor road and rail links, large areas of unrest, excessive border bureaucracy and petty corruption that have held back growth and integration.

Members have committed to eliminate tariffs on most goods, which will increase trade in the region by 15-25% in the medium term, but this would double if these other issues were dealt with, according to International Monetary Fund (IMF) estimates.

The IMF in a May report described a free-trade zone as a potential "economic game changer" of the kind that has boosted growth in Europe and North America, but it added a note of caution.

"Reducing tariffs alone is not sufficient," it said.

DIVERGENT INTERESTS

Africa already has an alphabet soup of competing and overlapping trade zones - ECOWAS in the west, EAC in the east, SADC in the south and COMESA in the east and south.

But only the EAC, driven mainly by Kenya, has made significant progress towards a common market in goods and services.