Resources sector service provider NRW Holdings Ltd (ASX:NWH) has been awarded a $35 million contract extension by a wholly owned subsidiary of Rio Tinto Ltd (ASX:RIO), Simfer SA.

The company said the contract is for earthworks at the Simandou Project in the Republic of Guinea in West Africa.

NRW has been undertaking works for Simfer SA at Simandou since 2007, with 120 staff in the country.

"Subject to formal execution, the contract will extend through to 31 December 2011," it said on Thursday.

The contract extension has an estimated minimum value of $35 million for the 12 month period.

NRW Holdings posted a $35.14 million profit in the 2010 financial year.

The Simandou iron ore province in Guinea is said to be the world's largest undeveloped iron ore deposit.