TOKYO, March 15 (Reuters) - Nissan Motor is considering seeking a business partnership with Honda Motor on key components for electric vehicles to cut production costs, three people familiar with the matter at Nissan said.

The potential partnership with domestic rival Honda could help Nissan gain economies of scale in producing EVs, which is crucial for Japanese automakers as they face heavy competition from China's BYD, Tesla and other electric vehicle makers.

The sources, who declined to be identified as the matter is still private, said Nissan and Honda are yet to formally start discussions, with the scope of the partnership undecided.

A Nissan spokesperson declined to comment. A Honda spokesperson said there was nothing the company could say.

The heads of the two automakers are due to hold a joint press conference in Tokyo at 3:30 p.m. (0630 GMT).

Another source said the idea of collaboration emerged between the chief executives of the companies.

Nissan is considering partnering with Honda on key EV parts, as well "kei car" - boxy vehicles that are smaller and less powerful than regular cars, primarily made for the domestic market.

The partnership could extend to overseas businesses, but that would affect Honda's existing collaboration with General Motors, according to two of the sources.

Nissan's pursuit of a partnership was first reported by TV Tokyo. The Nikkei newspaper has reported specific measures could include the introduction of a common powertrain, joint procurement and development of a common platform.

A source at Honda said a potential partnership with Nissan is one of many possibilities the company is considering, but there are many agenda that need to be sorted out for it to proceed with a new tie-up.

Honda is aiming to increase its ratio of electric vehicles and fuel cell vehicles to 100% of all sales by 2040.

Nissan already cooperates with Renault on EVs, mainly in Europe. The next Nissan electric Micra will share the same architecture as the new Renault Five and be built in the same plant in northern France.

Nissan has also committed to invest up to 600 million euros ($653 million) in Renault's new electric vehicle entity Ampere.

But the two firms last year reduced the scope of a years-long alliance to allow for a more agile partnership, and Renault has since signed agreements with new partners such as China's Geely. (Reporting by Maki Shiraki; Writing by Makiko Yamazaki; Additional reporting by Kantaro Komiya and Satoshi Sugiyama; Editing by Himani Sarkar, Michael Perry and Lincoln Feast.)