EXHIBIT A JOINT FILING AGREEMENT BETWEEN RIO TINTO PLC AND RIO TINTO INTERNATIONAL HOLDINGS LIMITED
EXHIBIT A
The undersigned hereby agree that the Statement on Schedule 13D, dated November 3, 2006, with
respect to the common shares, without par value, of Ivanhoe Mines Ltd. is, and any amendments
thereto executed by each of us shall be, filed on behalf of each of us pursuant to and in
accordance with the provisions of Rule 13d-1(k)(1) under the Securities and Exchange Act of 1934,
as amended, and that this Agreement shall be included as an Exhibit to the Schedule 13D and each
such amendment. Each of the undersigned agrees to be responsible for the timely filing of the
Schedule 13D and any amendments thereto, and for the completeness and accuracy of the information
concerning itself contained therein. This Agreement may be executed in any number of counterparts,
all of which taken together shall constitute one and the same instrument.
IN WITNESS WHEREOF, the undersigned have executed this Agreement as of the 3rd day
of November, 2006.
| Rio Tinto plc |
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| By: | /s/ ▇▇▇▇▇▇ ▇ ▇▇▇▇▇▇▇ | |||
| Name: | ▇▇▇▇▇▇ ▇ ▇▇▇▇▇▇▇ | |||
| Title: | Company Secretary | |||
| Rio Tinto International Holdings Limited |
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| By: | /s/ ▇▇▇▇▇▇ ▇ ▇▇▇▇▇▇▇ | |||
| Name: | ▇▇▇▇▇▇ ▇ ▇▇▇▇▇▇▇ | |||
| Title: | Director | |||