As they bitterly fought for the 2014, 2015 and 2016 championships at dominant Mercedes, the former friends became enemies.
"They were so bad that they didn't even say hello in the morning," Mercedes team chairman and Formula 1 legend Niki Lauda said.
After Rosberg beat Hamilton to the 2016 world championship, the German suddenly quit.
Rosberg said a month ago: "We were very good friends in the past, but it can happen again in the future.
"We're not rivals anymore, I'm completely out of it, so I don't see why we could not get along well after some time."
However, when pondering a rekindling of their friendship, the German admitted that he and Hamilton are currently "not at that point yet".
Hamilton has now told Stuttgarter Zeitung: "I last talked to Nico in Japan, but I do not invest any energy in changing our relationship."
The 32-year-old became a four-time world champion by securing the 2017 drivers' title.