Coal mining company Macarthur Coal (ASX:MCC) has forecast a significant profit slump for the first half of FY10, as a result of currency fluctuations.

The company said it expects an NPAT of $30 million to $38 million, compared to the $106.9 million reported in the first half of 2009.

The higher AUD/USD exchange rate and lower USD sale prices have been blamed for the expected slump.

Macarthur has maintained its sales target of 4.6 megatons of coal, but warned that the upcoming wet season may affect production and sales.