Global miner Rio Tinto Ltd (ASX:RIO) says it fears growing industrial activity in the resources sector could impact its iron ore mines.

In an internal memo obtained by The Australian newspaper, Rio Tinto iron ore boss Sam Walsh warned staff that last week’s illegal strike by 1,600 workers at Woodside Energy Ltd’s Pluto gas plant was “unnecessary”, and had affected Rio’s nearby iron ore export operations.

The miner is preparing to start bargaining with unions over workers’ pay and conditions for the first time in 15 years, after last month negotiating a new collective agreement with the Construction Forestry Mining and Energy Union.

But the union says the memo is “propaganda”, and that it is wrong of Mr Walsh to warn of possible industrial action before negotiations have even begun.

Rio Tinto posted a profit of $5.3 billion for 2008.