<PAGE>

                                                                 Exhibit 10.2(a)

                         INFONET SERVICES CORPORATION
                       1998 EMPLOYEE STOCK PURCHASE PLAN

                                 AMENDMENT TO
                      LOAN, SECURITY AND PLEDGE AGREEMENT
                      -----------------------------------

     This AMENDMENT TO LOAN, SECURITY AND PLEDGE AGREEMENT (this "Agreement") is
                                                                  ---------
entered into as of January 1, 2000 (the "Effective Date") by and between
                                         --------------
_____________________, an individual (the "Borrower"), and Infonet Services
                                           --------
Corporation, a Delaware corporation (the "Company"; the Borrower and the
                                          -------
Company, collectively, the "Parties").
                            -------

                                R E C I T A L S
                                ---------------

     WHEREAS, the Borrower and the Company have previously entered into a Loan
Pledge and Security Agreement (the "Agreement").

     WHEREAS, the Borrower and the Company wish to enter into an amendment to
the Agreement to permit the Borrower to transfer some of the Shares pledged
pursuant to the Agreement.

     NOW, THEREFORE, in consideration of the premises and mutual promises herein
made, and in consideration of the representations, warranties, and covenants
herein contained, the Parties agree as follows.

     1.   Section 4 of the Agreement is hereby deleted and replaced in its
entirety by the following:

          "1.  Pledge of Shares.  The Borrower hereby (a) pledges and deposits
               ----------------
     as security with the Company that number of the Shares as the Company may
     deem necessary for such security (the "Pledged Shares") and agrees to
     deliver to the Company certificates therefor accompanied by stock powers
     duly executed in blank by the Borrower and (b) assigns, transfers,
     hypothecates, mortgages, charges and sets over to the Company all of the
     Borrower's right, title and interest in and to the Pledged Shares (and in
     and to the certificates or instructions evidencing such Pledged Shares), to
     be held by the Company upon the terms and conditions set forth in this
     Agreement.  A copy of the form stock power is attached hereto as Exhibit 1.

          1.1  Dividends.  Until payment in full at maturity of the Loan, all
               ---------
               dividends and other amounts received by the Company as a result
               of the Company's record ownership of the Pledged Shares (if any)
               shall be applied to the repayment of the Loan.

          1.2  Voting Rights.  Until payment in full at maturity of the Loan,
               -------------
               and as long as the Borrower is not in default in the performance
               of any of the terms of this Agreement, the Borrower shall have
               the right (if any) to vote the Pledged Shares on all corporate
               questions; provided, however, that no vote
<PAGE>

               shall be cast on any action taken which would violate or be
               inconsistent with the terms of this Agreement or which would
               have the effect of materially impairing the position or
               interests of the Company.  The Company shall execute due and
               timely proxies in favor of the Borrower to this end.

          1.3  Adjustments.  In the event that, prior to payment in full at
               -----------
               maturity of the Loan, any share dividend, reclassification,
               readjustment, or other change is declared or made in the capital
               structure of the Company, all new, substituted, and additional
               Pledged Shares or other securities issued by reason of any change
               shall be held by the Company in addition to, or in substitution
               for, as the case may be, and in the same manner as the Pledged
               Shares.

          1.4  Warrants and Rights.  In the event that, prior to payment in full
               -------------------
               at maturity of the Loan, subscription warrants or any other
               rights or pledges shall be issued in connection with the Pledged
               Shares, such warrants, rights, and pledges shall be immediately
               assigned by the Company to the Borrower, and if exercised by the
               Borrower, all new shares or other securities so acquired by the
               Borrower shall be immediately assigned to the Company to be held
               in the same manner as the Pledged Shares.

          1.5  Repayment of the Loan.  On payment in full at maturity of the
               ---------------------
               Loan, the Company shall transfer to the Borrower all of the
               Pledged Shares and all rights received by the Company as a result
               of the Company's record ownership of the Pledged Shares.

          1.6  Default.  In the event that the Borrower defaults in the
               -------
               performance of any of the terms of this Agreement, the Company
               shall (a) be entitled to vote all or any part of the Pledged
               Shares and otherwise act with respect to the Pledged Shares as if
               it were the outright owner thereof (Borrower hereby irrevocably
               constituting and appointing Company the proxy and attorney-in-
               fact of the Borrower) and (b) have the rights and remedies
               provided in the California Commercial Code.  In this connection,
               the Company may, on five days' written notice to the Borrower,
               and without liability for any diminution in price that may have
               occurred, sell the Pledged Shares in a commercially reasonable
               manner and for such a commercially reasonable price as the
               Company may determine.  At any bona fide public sale, the
               Borrower shall be free to purchase all of any part of the Pledged
               Shares.  Out of the proceeds of any sale the Company may retain
               an amount equal to outstanding balance of the Loan, plus the
               amount of the expenses of the sale, and shall pay any balance of
               such sale to the Borrower.  If the proceeds of the sale are
               insufficient to cover the outstanding balance of the Loan plus
               expenses of the sale, the Borrower shall remain liable to the
               Company for any deficiency, in accordance with the provisions set
               forth in Commercial Code Section 9504.

                                      -2-
<PAGE>

     2.  Capitalized terms used but not defined in this Amendment shall have the
meanings assigned to them in the Agreement.

     IN WITNESS WHEREOF, the Parties hereto have executed this Agreement as of
the date first above written.

                                    Infonet Services Corporation



                                    By:____________________________

                                      Name:

                                      Title:

                                    The Borrower



                                      ____________________________
                                      Name

                                      -3-