Exhibit 99.1

               iBasis and KPN Extend Outside Date of Transaction

     BURLINGTON, Mass.--(BUSINESS WIRE)--Dec. 18, 2006--iBasis (NASDAQ: IBAS),
the global VoIP company, and Royal KPN N.V., the national carrier of the
Netherlands, today announced an amendment to their definitive agreement,
announced June 21, 2006, which extends the outside date for completion of the
transaction from December 31, 2006 to April 30, 2007.

     In addition to extending the transaction deadline, in the amendment iBasis
has agreed to provide KPN with regular updates and information on its stock
option grant review, including accounting, tax, regulatory and legal proceedings
and developments. Except for these amendments, the definitive agreement remains
unchanged and the parties have not waived any rights under the contract.

     On June 21, 2006, iBasis and KPN signed a definitive agreement to merge
KPN's international wholesale voice business into iBasis. The combination will
establish iBasis as one of the five largest international wholesale voice
carriers in the world, with combined 2005 revenues exceeding USD 1.1 billion and
more than 15 billion combined minutes in 2005. iBasis will acquire KPN
subsidiary KPN Global Carrier Services and receive USD 55 million in cash from
KPN in return for the issuance of approximately 40 million shares of iBasis
common stock, which represent a 51 percent ownership interest in iBasis on a
diluted basis. iBasis shareholders of record immediately prior to closing will
receive a cash dividend of USD 113 million immediately following closing.

     About iBasis

     Founded in 1996, iBasis (NASDAQ: IBAS) is a leading wholesale carrier of
international long distance telephone calls and a provider of retail prepaid
calling services, including the Pingo(R) web-based offering (www.pingo.com) and
disposable calling cards that are sold through major distributors and available
at retail stores throughout the U.S. iBasis customers include many of the
largest telecommunications carriers, including AT&T, Verizon, China Mobile,
China Unicom, IDT, Qwest, Skype, Telecom Italia, and Telefonica. iBasis carried
7.8 billion minutes of international voice over IP (VoIP) traffic in 2005, and
is one of the largest carriers of international voice traffic in the world(1).
For four consecutive years service providers have named iBasis the best
international wholesale carrier in ATLANTIC-ACM's annual International Wholesale
Carrier Report Card(2). The Company can be reached at its worldwide headquarters
in Burlington, Massachusetts, USA at 781-505-7500 or on the Internet at
www.ibasis.com.

     Safe Harbor Statement

     Except for historical information, all of the expectations, plans and
assumptions contained in the foregoing press release constitute forward-looking
statements under Section 21E of the Securities Exchange Act of 1934 and involve
risks and uncertainties. Statements regarding the proposed transaction between
the Company and Royal KPN, including the expected timetable for completing the
transaction, the expected dividend payment, future financial and operating
results, benefits and synergies of the transaction, future opportunities for the
combined company and products and any other statements regarding the parties'
future expectations, beliefs, goals or prospects, also constitute
forward-looking statements. Important factors that could cause actual results to
differ materially from such forward-looking statements include, but are not
limited to, (i) the Company's ability to execute its business plan; (ii) the
extent of adoption of the Company's services and the timing and amount of
revenue and gross profit generated by these services; (iii) fluctuations in the
market for and pricing of these services; (iv) the success of the Company's
plans to contest the FCC ruling on prepaid calling cards; (v) the ability of the
Company and Royal KPN to consummate the proposed transaction due to regulatory
restrictions, the failure to receive shareholder approval, the ability to
successfully integrate their operations and employees, the ability to realize
anticipated synergies, the emergence of new competitive initiatives resulting
from rapid technological advances or changes in pricing in the market, business
conditions and volatility and uncertainty in the markets that the Company and
Royal KPN serve, (vi) the Company's inability to meet the requirements of the
NASDAQ Stock Market for continued listing of the Company's shares; and (vii) the
other factors described in the Company's Quarterly Report on Form 10-Q for its
most recently completed fiscal quarter and Annual Report on Form 10-K for its
most recently completed fiscal year and Royal KPN's Annual Report on Form 20-F
for its most recently completed fiscal year all of which are available at
www.sec.gov. Such forward-looking statements are only as of the date they are
made, and we have no current intention to update any forward-looking statements.

     This communication may be deemed to be solicitation material in respect of
the proposed transaction between iBasis and Royal KPN. In connection with the
proposed transaction, iBasis intends to file relevant materials with the SEC,
including a proxy statement on Schedule 14A. SHAREHOLDERS OF IBASIS ARE URGED TO
READ ALL RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING IBASIS'S PROXY
STATEMENT, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED
TRANSACTION. Investors and security holders will be able to obtain the documents
free of charge at the SEC's web site, http://www.sec.gov, and iBasis's
shareholders will receive information at an appropriate time on how to obtain
transaction-related documents for free from iBasis. Such documents are not
currently available.

     Participants in Solicitation

     Royal KPN and its directors and executive officers, and iBasis and its
directors and executive officers, may be deemed to be participants in the
solicitation of proxies from the holders of iBasis Common Stock in respect of
the proposed transaction. Information about the directors and executive officers
of Royal KPN is set forth in the Annual Report on Form 20-F for the year ended
2005, which was filed with the SEC on March 14, 2006. Information about the
directors and executive officers of iBasis is set forth in iBasis's proxy
statement for its 2006 Annual Meeting of Shareholders, which was filed with the
SEC on March 23, 2006. Investors may obtain additional information regarding the
interest of such participants by reading the proxy statement regarding the
transaction when it becomes available.

     iBasis and Pingo are registered marks; the global VoIP company and The
iBasis Network are trademarks of iBasis, Inc. All other trademarks are the
property of their respective owners.

     (1) Telegeography 2006 data compared with iBasis 2005 traffic volume.

     (2) ATLANTIC-ACM International Wholesale Carrier Report Card - 2002, 2003,
2004, & 2005.


     CONTACT: Media:
              iBasis, Inc.
              Chris Ward, 781-505-7557
              cward@ibasis.net
              or
              Investors:
              iBasis, Inc.
              Richard Tennant, 781-505-7409
              ir@ibasis.net