The Dream Team VI have begun training in Atlanta, Georgia in the United States of America on Tuesday.
Samson Siasia will be keen to iron out flaws within his squad, following a 1-0 loss to Mexico in a friendly game last week.
The players in the US camp include captain Azubuike Okechukwu, Usman Mohammed, Saturday Kaego, Ndifreke Effiong, Sincere Seth, Emmanuel Daniel and Taiwo Awoniyi.
Others are Godwin Saviour, Shehu Abdullahi, Abdulrahman Taiwo and Junior Ajayi.
The team is expected to play two more friendlies against a local side and Honduras' U-23 team, before a final squad of 18 players leave for Brazil on July 29.