SYDNEY (Reuters) – Global miner Xstrata threatened to scrap $5.4 billion in Australian coal and copper projects, blaming a new mining tax and taking the value of new developments put on hold to above $20 billion in just a month.

Xstrata's move, which targets Prime Minister Kevin Rudd's home state of Queensland, will further pile pressure on the government to water down a proposed 40 percent tax on mining profits and give new ammunition to the tax's political opponents.

Xstrata, which last month halted some copper exploration in Queensland, said it was now shelving A$586 million of spending on its Wandoan thermal coal project and its expansion of its Ernest Henry copper mine.

That spending is part of a total planned capital investment of around A$6.4 billion ($5.4 billion) to complete both the Queensland developments, with the coal project accounting for the vast majority of this, the company added.