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 LETTERHEAD]

TENARIS ISSUES UPDATE ON ITS EXCHANGE OFFER

Luxembourg, November 18, 2002 - Tenaris S.A. ("Tenaris"), confirmed today that,
in connection with its offer to exchange its ordinary shares and ADSs for shares
and ADSs of Siderca S.A.I.C. ("Siderca") and Tubos de Acero de Mexico S.A.
("Tamsa") and shares of Dalmine S.p.A. ("Dalmine"), it has obtained all the
approvals required from Consob, the Italian securities regulator, and Borsa
Italiana and has made effective its offer to exchange its ordinary shares for
all outstanding ordinary shares of Dalmine S.p.A. ("Dalmine").

Tenaris also informed that, as of this date and in accordance with applicable
law, the board of directors of each of Siderca, Tamsa and Dalmine have already
determined, and made public, their respective positions regarding the exchange
offer.

     -   On October 30, 2002, the board of directors of Dalmine stated its
         position in favor of the exchange offer with respect to Dalmine and
         indicated that the proposed exchange ratio for the exchange of Tenaris
         shares for Dalmine shares is fair to Dalmine shareholders.

     -   On November 11, 2002, the board of directors of Tamsa expressed its
         favorable opinion that the exchange offer was fair to Tamsa's minority
         shareholders.

     -   On November 14, 2002, the board of directors of Siderca stated that it
         considered that the acceptance of the exchange offer from Tenaris
         should be beneficial to Siderca's shareholders.

The exchange offer, whose launch was announced on November 11, 2002, is made
subject to the terms and conditions established in the relevant prospectuses and
will close at 5:00 p.m. New York City time on December 13th, 2002. For
information on the exchange offer, please see www.tenarisexchange.com.

This press release is neither an offer to purchase nor a solicitation of an
offer to sell shares or ADSs. The exchange offer is made solely by the relevant
prospectuses, and the related forms of acceptance and letters of transmittal and
is not being made to, nor will tenders be 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. In those jurisdictions where the applicable laws require that the
exchange offer be made by a licensed broker or dealer, the exchange offer shall
be deemed to be made on behalf of the dealer manager or one or more registered
brokers or dealers licensed under laws of such jurisdiction.