The decision has been taken apparently to ensure continuity and speedy implementation of UPA government's flagship programmes.
The sources said that Manmohan Singh last week asked Narayanan and Nair to continue in their posts which were co-terminus with that of the Prime Minister.
Narayanan, a former chief of the Intelligence Bureau, was appointed to the powerful post of NSA in 2005.
Nair, a retired IAS officer of the Punjab cadre, was made the Principal Secretary to the Prime Minister in 2004.
The government had on Monday given one year extension to Cabinet Secretary K M Chandrasekhar, who was due to retire in a fortnight's time.
Government is also likely to take a decision on the tenure of Shyam Saran, Special Envoy to the Prime Minister.
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