Parliament's joint standing committee on defence says it will ask Defence Minister Nosiviwe Mapisa-Nqakula for more information around the deployment of 441 soldiers for the State of the Nation Address (Sona).

MPs on Friday adopted the letter President Jacob Zuma had sent on February 2, alerting Parliament to the deployment of the soldiers during Sona for the purposes of maintaining "law and order".

Democratic Alliance (DA) MP Sarel Marais wanted to know if it would have been possible for Zuma to have informed the committee sooner, seeing as it was "technically" in session during the week the letter was sent.

He also wanted to discuss the fact that the soldiers were patrolling in the precinct on the night of Sona, despite assurances from Speaker Baleka Mbete and Secretary to Parliament Gengezi Mgidlana that their duties would be ceremonial.

He said there were clear differences between what was promised and what happened on the night.

African National Congress (ANC) MP Mnyamezeli Booi said the committee was not in a position to answer those questions, and suggested Mapisa-Nqakula be asked if she would attend a committee meeting to elaborate.

ANC MP Dennis Gamede said it would be more appropriate for the presiding officers to also supply details around the signing off on the 441 soldiers and their duties on the night.

DA MP Shahid Esau said there is nothing the committee can do about the letter now other than to accept it as a formality. He said the committee should focus on getting answers from the ministry.

Joint chairperson Emmanuel Mlambo said the committee will ask the minister for a meeting.

It will write to Mbete and National Council of Provinces chairperson Thandi Modise for their input on the letter and the use of the army's services on the night.