SPLM-North spokesperson Arnu Ngutulu Lodi said on Friday the group is committed to international standards that forbid the use of children under 18 years.
The SPLM-North has been battling Sudanese government forces in South Kordofan state since June 2011, following disputed gubernatorial elections.
The conflict has displaced tens of thousands across the state and more than 60 000 have fled to Yida refugee camp in South Sudan.
Khartoum says SPLM-North is backed by South Sudan which gained independence from Sudan last year.
SPLM-North was reacting to comments made by the United States Assistant Secretary of State Anne C Richard, during an October 31 visit to South Sudan.