Fernandes was hospitalised in July after suffering a fall while doing yoga at his house.
Nearly 10,000 people, mostly Keralite Christians, are expected to participate in the canonisation of Sister Alphonsa in Vatican on October 12.
The current spell of the ceasefire will end on July 31.
"This time, we want something concrete from the government on our demands. Otherwise it is futile to meet only for the extension of the ceasefire," NSCN-IM spokesman Tongmeth Wangnao Konyak told PTI on phone.
The medicos have not yet called off their strike.
Govt-NSCN (IM) talks in Amsterdam on Tuesday
May 27 is the last date for filing nomination papers and June 3 is the deadline for withdrawal.
With an aim to boost the ongoing Naga peace process, a central team including three Union ministers began a crucial round of negotiations with Nationalist Social Council of Nagalim (Isak-Muivah) leaders at the Hague on Thursday.
The NSCN (IM) has been operating from South Asian territories since nearly four decades. It entered into a ceasefire agreement with the government in 1997.
But Congress' Kiran Chaudhary and BJP's Shakuntala Hegde lost in a close contest in the biennial elections.
Information and Broadcasting Minister Manish Tewari, who is not contesting Lok Sabha polls as he is ailing, has been made acting in-charge of the AICC Communication department along with party spokesman Randeep Surjewala.
Ahead of the crucial All India Congress Committee session on Friday, Union Minister Oscar Fernandes on Thursday said Rahul Gandhi is Congress candidate for Prime Ministership even as suspense remains on whether the party will formally anoint him as PM nominee for the Lok Sabha polls.