Rebuking France in its annual report, the United States Commission on International Religious Freedom (USCIRF) –which advises the government - believes the French legislation could set a wrong precedent.
"The French government and legislature should be urged to reassess this initiative in light of its international obligations to ensure that every person in France is guaranteed the freedom to manifest his or her religion or belief in public, or not to do so," the panel's report underlined.
USCIRF expressed concern that other European countries might follow the French example and said Belgium and Germany were already weighing similar moves.
The French law, which becomes effective at the start of the next school year in September, bans students from wearing certain forms of religious clothing or symbols in public schools.
It bans Muslim hijabs, large crosses worn by Christians, Jewish skullcaps and Sikh turbans.
The measure sparked demonstrations by France's Muslim community and criticism from many Muslim countries.