EXHIBIT 99.12 LEVEL 3 COMMUNICATIONS, INC. Exchange Offer to holders of its 12 7/8% Senior Discount Notes due 2010 NOTICE OF GUARANTEED DELIVERY As set forth in the Prospectus dated , 2000 (the "Prospectus") of Level 3 Communications, Inc. (the "Company") under "The Exchange Offer--How to Tender" and in the Letter of Transmittal (the "Letter of Transmittal") relating to the offer (the "Exchange Offer") by the Company to exchange up to $675,000,000 in principal amount at maturity of its 12 7/8% Senior Discount Notes due 2010 (the "New Notes") for $675,000,000 in principal amount at maturity of its 12 7/8% Senior Discount Notes due 2010, issued and sold in a transaction exempt from registration under the Securities Act of 1933, as amended (the "Original Notes"), this form or one substantially equivalent hereto must be used to accept the Exchange Offer of the Company if: (i) certificates for the Original Notes are not immediately available; or (ii) time will not permit all required documents to reach the Exchange Agent (as defined below) on or prior to the expiration date of the Exchange Offer (as described in the Prospectus). Such form may be delivered by hand or transmitted by telegram, telex, facsimile transmission or letter to the Exchange Agent. TO: The Bank of New York (the "Exchange Agent") By Facsimile: (212) 815-6339 Confirm by telephone: (212) 815-2742 By Registered or Certified Mail: The Bank of New York 101 Barclay Street, 7E New York, New York 10286 Attention: Enrique Lopez By Overnight Courier or By Hand: The Bank of New York 101 Barclay Street Corporate Trust Services Window Ground Level New York, New York 10286 Attention: Enrique Lopez Delivery of this instrument to an address other than as set forth above or transmittal of this instrument to a facsimile or telex number other than as set forth above does not constitute a valid delivery. Ladies and Gentlemen: The undersigned hereby tenders to the Company, upon the terms and conditions set forth in the Prospectus and the Letter of Transmittal (which together constitute the "Exchange Offer"), receipt of which are hereby acknowledged, the principal amount at maturity of Original Notes set forth below pursuant to the guaranteed delivery procedure described in the Prospectus and the Letter of Transmittal. Sign Here Principal Amount at Maturity of Signature(s) ________________________ Original Notes _____________________________________ Tendered ________________________ Please Print the Following Certificate Nos. Information Name(s) _____________________________ (if available) __________________ _____________________________________ Total Principal Amount at Maturity Address _____________________________ Represented by Original Notes _____________________________________ Certificate(s) __________________ Area Code and Tel. No(s). ___________ Account Number __________________ ------------------------------------- Dated: ____________________, 2000 2 GUARANTEE The undersigned, a member of a recognized signature guarantee medallion program within the meaning of Rule 17A(d)-15 under the Securities Exchange Act of 1934, as amended, hereby guarantees that delivery to the Exchange Agent of certificates tendered hereby, in proper form for transfer, or delivery of such certificates pursuant to the procedure for book-entry transfer, in either case with delivery of a properly completed and duly executed Letter of Transmittal (or facsimile thereof) and any other required documents, is being made within three trading days after the date of execution of a Notice of Guaranteed Delivery of the above-named person. Name of Firm _________________________________ Authorized Signature _________________________ Number and Street or P.O. Box ________________ ______________________________________________ City State Zip Code ___________ Area Code and Tel. No. _______________________ Dated: , 2000 3