Takeover target Herald Resources Ltd has rebuffed claims by suitor PT Bumi Resources that the coal miner is better placed to develop the Dairi zinc project in Indonesia.
Bumi, Indonesia's largest coal producer, is offering $2.25 cash for every Herald share, valuing the company at $455 million.
Herald chairman Terry Allen said on Thursday the company was "concerned" about Bumi's statement that its experience in the Indonesian mining sector and the requirements of the regulatory process make it uniquely positioned to advance the Dairi project.
"Herald is not aware of any special circumstances which may uniquely position PT Bumi in securing the forestry approval required to develop the Dairi project or in any way disadvantage you as owners of the company relative to PT Bumi," Mr Allen said in a statement.
"In this regard we note that our 20 per cent joint venture partner in the Dairi project is PT Antam, which is one of Indonesia's largest mining companies.
"PT Antam is 65 per cent owned by the Indonesian government and is listed on the Jakarta and Australian stock exchanges."
The company has completed feasibility studies on the $US220 million ($A250.1 million) project but has been waiting for more than two years for specific environmental approvals to proceed with development.
The Indonesian minister of forestry has advised Herald that a presidential decree is required for the ministry to issue the necessary approvals for underground mining in forest areas.
Herald has advised its shareholders to take no action in relation to the unsolicited bid.
Bumi is backed by Indonesian cabinet minister Aburizal Bakrie.