But Ambassador Samantha Power today would not name those countries or detail their level of involvement.
She says more than 40 countries have spoken in support of the campaign against the Islamic State group, and they will announce their own plans in their own time.
French forces last week joined combat missions. Saudi Arabia has offered to help train moderate anti-Islamic State group fighters.
Power spoke today morning news programs as the U.N. General Assembly prepared a week of high-level meetings, many of them about the growing militants' threat in Iraq and Syria.