"I want France to accompany the creation of this force in a spirit of partnership", Macron said in opening comments.
A narrator speaking in English said the 17-minute video showed hostages from South Africa, France, Colombia, Australia, Romania and Switzerland.
The new anti-terror force will operate in the region along with a 12,000-strong United Nations peacekeeping mission in Mali, which has become the deadliest in the world, and France's own 5,000-strong Barkhane military operation, its largest overseas mission.
Some observers see the initiative of the G5 Sahel bloc - Mali, Mauritania, Burkina Faso, Niger and Chad - as forming the basis of an eventual exit strategy for around 4,000 French troops now deployed to the volatile region.
"We can not hide behind words, and must take actions", he said.
Although Chad's military is widely viewed as the strongest of the five Sahel nations, President Idriss Deby has said his country can not afford to mobilise large numbers of troops simultaneously for the UN peacekeeping mission and also in the new force.
The new Sahel force will support national armies trying to catch jihadists across porous frontiers, and its operations will be closely coordinated with Barkhane, a source in the French presidency told AFP.
The European Union already has pledged some 50 million euros ($57 million) in support of the new G5 force.
The speaker said: "No genuine negotiations have begun to rescue your children".
Today's meetings came a day after the recently formed extremist group Nusrat al-Islam wal Muslimeen, based in Mali, released a proof-of-life video showing six foreign hostages seized in the region in recent years. "And we will put all of our energies into eradicating them".
Macron also said France would provide 200 million euros in development assistance to the Sahel, a semiarid region stretching along the southern end of the Sahara, over the next five years.
Macron, who visited French troops in northern Mali during his first week in office, will attend a summit with African leaders as the force is formally launched.