Election commission chairman Mahinda Deshapriya and members N.J. Abeysekara and S. Ratnajeevan Hoole have signed it.
Fonseka will take oaths when parliament meets this afternoon (09), said leader of the House Lakshman Kiriella.
The UNP working committee yesterday approved Fonseka to be appointed to fill the vacancy created following the death of minister M.K.A.D.S. Gunawardena.
Fonseka is expected to be given a powerful cabinet portfolio, according to UNP sources.
The UNP and the DP entered into a MoU on February 03.