Charlie Puth has said he tried to get Mac Miller "clean" before the rapper died aged 26 last week.
Miller, a platinum-selling US musician, was found unresponsive at his home in Los Angeles on Friday morning after a reported overdose.
American singer Puth, also 26, revealed the pair had become "really good friends" in the six months leading up to Miller's death.
Speaking to E! News, he said: "We talked almost every day and I don't get a lot of friends who come into my life who I hit it off with so quickly.
"I had known him for about six months, but we became really close, we became really good friends and I always thought I'd be the one to help him get clean and to lead him on to the path of a good, clean, sober life."
Following Miller's death, Puth, known for collaborating with Wiz Khalifa on the song See You Again, tweeted to say he had texted the rapper's phone.
He revealed the message read, "I love you man".
He said: "Every time someone close to me passes away I always text their phone and - I don't know why I do this often - I just wrote, 'I love you man', and I knew he wasn't going to write back but I just felt like I had to do it anyway."
Puth added: "He was one of a kind, there was no one like Mac."
The LA coroner said the cause of Miller's death is yet to be determined and that a post-mortem examination will be carried out.
In a statement, his family said Miller was a "bright light in this world for his family, friends and fans".
Ed Sheeran, Drake, Chance The Rapper and Post Malone were among a stream of stars to pay tribute to the "great talent", who released his fifth studio album, Swimming, in August.
Story by Keiran Southern, Press Association Los Angeles Correspondent