Such a delay would be the sixth for the programme, which aims to revive Japan's dormant commercial aviation industry.
A new first-delivery date could be set next month, the paper said on Saturday, without citing a source. The plane, this year renamed the SpaceJet instead of the Mitsubishi regional jet, was originally due to enter service in 2013.
Jefferies analyst Sho Fukuhara said in a note to clients that the delays, if confirmed, could trigger market concerns about Mitsubishi Heavy Industries Ltd, the planemaker's largest shareholder.
Mitsubishi Heavy told the stock exchange on Monday that the planemaker was putting its "utmost effort" into completing certification and was sharing information about the schedule with all relevant parties. It did not provide an update on the delivery schedule for the plane.
"There has been no official announcement or comment on our schedule," a Mitsubishi Aircraft spokesman said on Tuesday.
"As we are evaluating the long term schedule, we are doing so not only for the development, certification and delivery of our first aircraft, but ... also to make decisions that will benefit the long term success of commercial aviation in Japan," the spokesman said.
ANA Holdings Inc , Japan's largest airline by revenue, is due to be the first customer for the plane.
Nikkei said the manufacturer would probably begin to hash out compensation for the delay, which would push the entry into service beyond the Tokyo Summer Olympics next year.
An ANA spokesman declined to comment on potential delays but said the airline looked forward to having the SpaceJet in its fleet and providing its customers with a new regional jet.
(Reporting by Jamie Freed in Singapore; Additional reporting by Allison Lampert in Las Vegas and Tim Kelly in Tokyo; Editing by Clarence Fernandez, Stephen Coates and Tom Hogue)