Offer Update

Antofagasta PLC
23 March 2006

                                ANTOFAGASTA PLC

             Antofagasta increases cash takeover offer for Tethyan

LONDON: 23 March 2006 - Antofagasta PLC ('Antofagasta') announces that it has
today reached agreement with Tethyan Copper Company Limited ('Tethyan') to
revise the terms of its takeover offer for Tethyan ('the Offer') such that:

•  the offer price is increased to A$1.40 cash per Tethyan Share; and

•  all remaining conditions of the Offer have been waived by
   Antofagasta, other than conditions relating to Minimum Acceptance, Options,
   Prescribed Occurrences, Other Regulatory Approvals and Material Acquisitions,
   Disposals and Commitments.

The Offer represents an increase of 17% over Antofagasta's original offer price
of A$1.20 per share and is 5 cents per share higher than Skafell Pty Ltd's
hostile offer.

Antofagasta has the full support of its proposed joint venture partner, Barrick
Gold, in relation to the Offer.

The Board of Tethyan has unanimously recommended that shareholders should accept
the Offer in the absence of a superior offer emerging and has indicated that the
Tethyan directors will be accepting the Offer for all of their holdings of
Tethyan Shares they own or control on that basis.

Marcelo Awad, CEO of Antofagasta Minerals S.A., stated, 'Antofagasta's offer is
the highest offer for Tethyan in the market and is the only offer unanimously
recommended by the Board of Tethyan.  It represents a very attractive price for
Tethyan shareholders and I would encourage all shareholders to accept the Offer
as soon as possible.'

Antofagasta currently owns 14.85% of Tethyan's issued share capital.
Antofagasta wishes to confirm that, under no circumstances will this
shareholding be tendered into Skafell's offer, whilst it remains subject to a
90% acceptance condition.  This means that Skafell's offer as it currently
stands is not capable of succeeding.

Antofagasta also notes that under its agreement with BHP Billiton it may, at its
option, purchase the claw-back right over certain Tethyan mineral interests at
any time during the currency of its offer (following the satisfaction or waiver
of its Other Regulatory Approvals condition).  If Antofagasta purchases the
claw-back right it would have the right to acquire 70% of Tethyan's economic
interest in the Western Porphyries, which currently hosts the vast majority of
the contained copper-gold resource at Reko Diq.

Rothschild is advising Antofagasta in relation to this transaction.

End
                                                 Enquiries - Santiago
Enquiries - London
                                                 Antofagasta Minerals S.A.
Antofagasta PLC                                  Alejandro Rivera
Tel: [phone]                            Tel: [phone]
www.antofagasta.co.uk                            Email: [e-mail]

Desmond O'Conor                                  Enquiries - Australia
Email: [e-mail]

                                                 N M Rothschild & Sons 
                                                 (Australia) Ltd (financial 
                                                 advisers)
Bankside Consultants                             Tel: [phone]
Tel: [phone]                            Marshall Baillieu
Mob: [phone]                            Chris Forman

Keith Irons                                      Jackson Wells Morris 
                                                 (public relations advisers)
Email: [e-mail]                        Tel: [phone]
                                                 Benjamin Haslem
                                                 Jakob Webster


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