FILED BY TENARIS S.A.
                           PURSUANT TO RULE 425 UNDER THE SECURITIES ACT OF 1933

                                               SUBJECT COMPANY: SIDERCA S.A.I.C.
                                                  EXCHANGE ACT FILE NO.: 1-15188

                                 SUBJECT COMPANY: TUBOS DE ACERO DE MEXICO, S.A.
                                                  EXCHANGE ACT FILE NO.: 1-04870

                COMMISSION FILE NUMBER FOR THE REGISTRATION STATEMENT: 333-99769





[TENARIS PRESS RELEASE LOGO]

Tenaris Announces Successful Conclusion of its Exchange Offer

Luxembourg, December 16, 2002 - Tenaris S.A. ("Tenaris"), announced today that
its offer to exchange its ordinary shares and ADSs for shares and ADSs of
Siderca S.A.I.C. (MERVAL: ERCA and NYSE: SDT) ("Siderca"), shares and ADSs of
Tubos de Acero de Mexico S.A. (BMV: TAMSA and AMEX: TAM) ("Tamsa") and shares of
Dalmine S.p.A (MTA: D) ("Dalmine") was concluded successfully on December 13,
2002, and that trading is expected to begin this morning in its ordinary shares
on the Buenos Aires and Mexican stock exchanges and in its ADSs on the New York
Stock Exchange under the symbol TS. Trading in its ordinary shares on the
Mercato Telematico Azionario in Italy is expected to begin as from tomorrow.

As a result of the transaction, Tenaris will hold 99.11% of the capital stock of
Siderca, 94.50% of the capital stock of Tamsa and 88.41% of the capital stock of
Dalmine. Tenaris has accepted all the shares and ADSs tendered, having exercised
its right to waive the previously established threshold applicable to the
Dalmine shares.

Accordingly, Tenaris will have a total of 1,160,700,793 shares issued and
outstanding, with 61.23% held by Sidertubes S.A., a Techint group company, and
38.77% held by the public.

As a result of Tenaris's new ownership level in Siderca and Tamsa, in accordance
with Argentine and Mexican laws, Tenaris is entitled, and may also be required,
to make further offers to the investors that did not exchange their shares,
which may ultimately lead to the delisting of the shares of Siderca and Tamsa.
Tenaris intends to commence the necessary proceedings to that end shortly.
Similarly, Tenaris has committed with Borsa Italiana to take steps aimed at
causing the delisting of Dalmine within the next 12 months.

Tenaris, a corporation organized in Luxembourg, is a leading manufacturer and
supplier of seamless steel pipe products and associated services to the oil and
gas, energy and other industries. Tenaris's operating subsidiaries include eight
established steel pipe manufacturers: AlgomaTubes, Confab, Dalmine, NKKTubes,
Siat, Siderca, Tamsa and Tavsa.

Tenaris wishes to thank all those shareholders of Siderca, Tamsa and Dalmine who
elected to participate in the exchange offer for their confidence in Tenaris.

More information about Tenaris is available at www.tenaris.com. Information on
or accessible through this website is not part of this press release.

THIS COMMUNICATION IS NEITHER AN OFFER TO PURCHASE NOR A SOLICITATION OF AN
OFFER TO SELL SHARES OR ADSS. THE EXCHANGE OFFER WAS MADE IN ARGENTINA, ITALY,
MEXICO AND THE UNITED STATES SOLELY BY THE PROSPECTUSES DATED NOVEMBER 7, 13, 11
AND 8, 2002, RESPECTIVELY, AND THE RELATED FORMS OF ACCEPTANCE AND ADS LETTERS
OF TRANSMITTAL AND WAS NOT MADE TO, NOR WERE TENDERS ACCEPTED FROM OR ON BEHALF
OF, HOLDERS OF SHARES OR ADSS IN ANY JURISDICTION IN WHICH THE MAKING OF THE
EXCHANGE OFFER OR ACCEPTANCE THEREOF WOULD NOT BE IN COMPLIANCE WITH THE LAWS OF
SUCH JURISDICTION.