A nation has to invest in its security, President Jacob Zuma said on Friday.

"We will not be found wanting in this regard for the instability in our continent presents a direct national security threat to us," Zuma told a parade celebrating the country's tenth year in peace support operations in Bloemfontein.

Zuma said there are those who believe that the intensifying of democracy in any country reduces the security threat and that there was no need to invest in defence in a democracy such as South Africa.

"This is a mistake," he said.

This follows reports this week that government was racing against time to decide on the acquisition of eight Airbus A400M military transport aircraft, with the price rising significantly from R17-billion to about R47-billion.

Airbus Military said, in a statement, it was still in ongoing discussions with the South African authorities regarding developments with the A400M programme.

However, the Democratic Alliance on Friday called on Defence and Military Veterans Minister Lindiwe Sisulu to reveal details of the Airbus A400M military transport aircraft acquisition.

On Friday, Zuma said the existence of conflict in many regions in the world indicated that democracy within South Africa's borders was not a guarantee of national security.

He said a defence force plays a critical role in creating an environment of peace and stability in which to consolidate democracy.

"Our defence force plays an additional role as it has continental responsibilities as well. It therefore has to be capacitated appropriately to play that role."

Zuma said South Africa's defence force creates an environment that was conducive for reconstruction and development and faster economic development in the region.