The United States is rejecting a call from U.N. Secretary-General Antonio Guterres for the world body to fund a new 5,000-troop African force meant to fight extremists in western Africa's vast Sahel region.

Guterres says in a report to the Security Council that the Sahel force should receive regular U.N. funding instead of voluntary contributions, and he is urging West African countries to speed up its deployment.

But U.S. political coordinator Amy Tachco told the council Wednesday that the U.S. objects in principle to a U.N. mandate for the force "or the use of U.N. assessed funds for the force."

The so-called "Group of Five" nations comprising the force — Mali, Niger, Burkina Faso, Mauritania and Chad — have been grappling with a growing menace from extremists.