The Japanese companies’ decision to call off negotiations highlights the challenges legacy automakers face in partnering to tackle new technologies.

TOKYO—Honda and Nissan on Thursday officially scrapped their planned merger less than two months after announcing it, putting pressure on troubled Nissan to look for other partnerships.The two Japanese automakers had said in December that they planned to combine operations by 2026,

Japanese automaker Honda is reporting a 7% decline in profit for the nine months that ended in December as it terminated talks on business integration with Nissan.