"The fight of the Iraqis against terrorism is our fight as well," Hollande told representatives from around 30 countries and organisations, urging "clear, loyal and strong" global support for Iraq.
Iraqi President Fuad Masum also stressed the urgency of firm action, as the beheading of a third Western hostage in the run-up to the conference stepped up the pressure on the international community to destroy the Islamic State (IS) extremist group.
"We are still asking for regular aerial operations against terrorist sites. We have to pursue them wherever they are. We need to dry up their sources of finance," added the Iraqi leader.
As if to underscore the urgency of the campaign, France announced just hours ahead of the conference that it was joining Britain in carrying out reconnaissance flights in support of the US air campaign against the jihadists.
Shortly afterwards, two French Rafale fighter jets took off from the base, an AFP correspondent reported.
During the conference, US Secretary of State John Kerry will seek to fine-tune the strategy of the US-led coalition against IS, following a marathon tour through the Middle East to drum up support.
He told CBS's Face the Nation that "all bases were covered" in the coalition with some allies offering air strikes and others boots on the ground.
"Every single aspect of the president's strategy, and what is needed to be done in order to accomplish our goal, has been offered by one country or multiple countries, and all bases are covered," Kerry said.
