Japanese giant Nippon Steel says the Queensland government’s coal royalties grab influenced its decision to spend $1 billion buying a stake in Whitehaven’s Blackwater coking coal mine, amid rising concerns over supply security.

Nippon Steel and Japanese company JFE Steel collectively bought 30 per cent of Blackwater in a deal disclosed on Thursday, giving owner Whitehaven Coal a $US1.1 billion ($1.6 billion) cash injection.