The United Nations chief condemned "appalling allegations" of child sexual abuse by French soldiers in Central African Republic while meeting with worried countries that included two of the world body's top funders.

Also on Friday, the ambassador for the United States, by far the U.N.'s top contributing country, welcomed a new external review into how the allegations were handled.

Confidential documents have shown that the U.N.'s top human rights officials did not follow up for more than half a year on allegations collected by their own staffers, while French authorities pressed for more information. France opened a formal judicial inquiry just last month.

Ban Ki-moon met Friday with Australia, Japan, Norway and Guatemala, who did not comment shortly afterward. Japan is the U.N.'s second-largest funder, contributing 10 percent of the world body's regular budget. Australia also falls in the top dozen contributors.

The United States, which did not attend, pays 22 percent of the U.N.'s regular budget. U.S. Ambassador Samantha Power in a statement Friday said the external review into the child sexual abuse allegations is a chance "to learn what went wrong at every point in this process." The foreign minister of Canada, another top contributor, issued a statement Thursday expressing outrage over the allegations.

Few details have been announced about the external review, which will address both the specific allegations and wider issues related to how the U.N. responds to such sensitive claims. Ban's spokesman has said a summary of the findings will be made public.

A person familiar with Friday's meeting said key details like who would lead the review and how long it would take still had not been decided. The person, who spoke on condition of anonymity because the meeting was private, said many more countries than the four member states that attended have concerns.

Ban's spokesman, Stephane Dujarric, told The Associated Press that Ban told the diplomats that "our central concern must be to protect the rights and well-being of victims of these abuses and to ensure that the perpetrators are held to account."