The French president has called for Africa to be given a bigger say in world affairs and better representation on the UN Security Council.
President Nicolas Sarkozy, rounding off a two-day France-Africa summit in Nice, also said Africa would be a key source of global growth in the coming decades.
He pledged to push for Security Council reform when France heads the G8 and G20 groups of leading economies next year.
The summit was attended by 38 heads of state and some 200 business leaders.
Mr Sarkozy told them: "How can we accept a world where 25% of the population lives in Africa and yet it does not have a permanent seat at the Security Council?
"This is an anomaly, an injustice and a source of imbalance."
At present, African countries hold three out of 10 non-permanent seats on the Security Council.
African states have lobbied since 2005 for two permanent seats with veto powers on an expanded Security Council, as well as rotating seats.
"None of the problems, absolutely none of the problems that the world faces today can be resolved without the active participation of the African continent," Mr Sarkozy said.
"Africa's formidable demographics and its considerable resources make it the main reservoir for world economic growth in the decades to come."
Hosting his first France-Africa summit, Mr Sarkozy dispensed with the traditional "dinner among friends" - attended only by former colonies - in favour of inviting all attendees.
"France doesn't just want to be friends with Francophone countries. What we want is for France to talk to all of Africa," he said at the closing session.
France, which is vying with China and other emerging powers for markets in Africa, has used the summit as a platform to promote business ties with the continent.
It agreed to support the African Union in strengthening security on the continent, including training 12,000 African troops for African Union and United Nations peacekeeping duties.
Climate change was also high on the agenda and the leaders agreed to support creation of a renewable energy plan, including the use of solar power.
France announced the creation of the African Agriculture Fund, an investors' fund, for food distribution and other projects, to initially raise $120 million (£82m) and potentially reach $300 million, according to a final statement.
It also pledged to help Africa combat piracy, terrorism and drug trafficking, with Mr Sarkozy stressing the continent "cannot cope on its own".
South African President Jacob Zuma described the summit as "very useful".
He told AFP news agency that leaders had agreed to discuss at their next African Union summit a French proposal to seek two Security Council seats with 10-year mandates as an interim step to permanent membership.
"We cannot have institutions that were established in the 1940s, when there were fewer countries and colonialism," he said.
Mr Zuma had earlier criticised the fact that military junta leaders of two former French colonies, Guinea and Niger, were among those in attendance and as such were being given "recognition".
However, Madagascar - still embroiled in a political crisis - was not invited, and Zimbabwe refused to send a delegation after France objected to the attendance of President Robert Mugabe.