Diatreme Resources has extended its off-market takeover bid for Metallica Minerals (ASX:MLM) until June 3.

The extension, prompted by increased acceptances, boosts Diatreme's stake in Metallica to 44.26%.

The offer is declared "best and final" unless a competitive bid arises.

CEO Neil McIntyre urges remaining shareholders to accept the offer, emphasising its value and finality.