Dave Mustaine accused Metallica drummer Lars Ulrich of being afraid to tour with Megadeth in a recent interview that appeared to restart the feud between the pair.

Mustaine also reiterated that he had no interest in helping Metallica release their No Life ’til Leather demo while a disagreement over writing credits remained between them – and alleged that James Hetfield was afraid of Ulrich.

A replica of the 1982 tape was released for Record Store Day 2015, and Metallica promised an extended version would follow. When that failed to materialize, it emerged that Mustaine, who played a significant role in writing and performing on the seven-track title, had refused to give permission for the release to go ahead.

“I won’t give them my rights, so I will not be part of it,” Mustaine told Greece’s Rock Hard (via Google Translate, edited for clarity). “I wrote all of ‘Mechanix’ and ‘Jump in The Fire’ and I won’t give anything to Lars Ulrich. He can give it up. With ‘Phantom Lord’ I wrote all the music and James Hetfield did all the lyrics – 50/50. If James wants to give his share to Lars because he’s scared of him, that's up to him. I'm not afraid of Lars Ulrich and I won’t give him my share.”

He continued: “The same happened with ‘Metal Militia.’ I wrote every note of the song and James wrote all the lyrics. If James wants to give his share to Lars because he’s afraid of him, that’s OK. I'm not afraid of him. I'm not giving anything to Lars Ulrich. Everyone knows they got the rights in the past. But the past is past. But I can’t willingly come to an agreement with these people and give Lars credit for something that he not only didn’t do – but was also incapable of doing. He couldn’t write songs so good then.”

The dispute clearly puts a question mark over the chances of any future Big Four concerts featuring Metallica, Megadeth, Slayer and Anthrax. But Mustaine argued: “it’s not about the Big Four. I believe Lars is afraid to play with Megadeth.”

The guitarist, who was fired by Metallica in 1983, has previously admitted he started Megadeth as an act of “revenge.” Asked about feeling anger, he replied: “I don’t think it is or should be the only motivation. Anger, as Johnny Rotten once said, is an act. And I know that when I'm angry, I can do things I never thought I could do. It’s like when mothers see that their child is in danger and suddenly gain superhuman powers.” Referring to his own motivation he added: “I don’t think that’s the case.”

Megadeth just released a new extended version of debut album Killing Is My Business… and Business Is Good, subtitled The Final Kill.