In the preceding table, the Corporation’s supply commit- ments include its estimated purchases of 50% of HOVENSA’s production of refined products, after anticipated sales by HOVENSA to unaffiliated parties. Also included are normal term purchase agreements at market prices for additional gasoline necessary to supply the Corporation’s retail market- ing system and feedstocks for the Port Reading refining facility. In addition, the Corporation has commitments to purchase natural gas for use in supplying contracted cus- tomers in its energy marketing business. These commitments were computed based on year-end market prices. The table also reflects that portion of the Corporation’s planned capital expenditures that are contractually commit- ted at December 31. The Corporation’s 2004 capital expen- ditures are estimated to be approximately $1.5 billion, including approximately $900 million for oil and gas develop- ments. Obligations for operating expenses include commit- ments for transportation, seismic purchases, oil and gas production expenses and other normal business expenses. Other long-term liabilities reflect contractually committed obligations on the balance sheet at December 31, including minimum pension plan funding requirements. In connection with the sale of six vessels in 2002, the Cor- poration agreed to support the buyer’s charter rate on these vessels for up to five years. The support agreement requires that if the actual contracted rate for the charter of a vessel is less than the stipulated support rate in the agreement, the Corporation will pay to the buyer the difference between the contracted rate and the stipulated rate. The balance in the charter support reserve at December 31, 2003 was $32 million. The Corporation has a contingent purchase obligation to acquire the remaining 50% interest in a retail marketing and gasoline station joint venture for $88 million. The Corporation guarantees the payment of up to 50% of HOVENSA’s crude oil purchases from suppliers other than PDVSA. The amount of the Corporation’s guarantee fluctu- ates based on the volume of crude oil purchased and related prices and at December 31, 2003 amounted to $134 million. Foreign Operations: The Corporation conducts explo- ration and production activities in many foreign countries, including the United Kingdom, Norway, Denmark, Gabon, Indonesia, Thailand, Azerbaijan, Algeria, Malaysia and Equatorial Guinea. Therefore, the Corporation is subject to the risks associated with foreign operations. These expo- sures include political risk (including tax law changes) and currency risk. The effects of these events are accounted for when they occur and generally have not been material to the Corporation’s liquidity or financial position. See also  GLYPH<210>Contractual Obligations and ContingenciesGLYPH<211> above, Note No. 7, “Refining Joint Venture,” and Note  No. 18, “Guarantees and Contingencies,” in the financial statements. Off-Balance Sheet Arrangements: The Corporation has leveraged lease financings not included in its balance sheet, primarily related to retail gasoline stations that the Corporation operates. The net present value of these financings is $462 million at December 31, 2003, using interest rates inherent in the leases. The Corporation’s December 31, 2003 debt to capitalization ratio would increase from 42.5% to 45.2% if the lease financings were included. *Includes $40 million HOVENSA debt guarantee discussed above. The remainder relates principally to a loan guarantee for a natural gas pipeline in which the Corporation owns a 5% interest. In addition, the Corporation has agreed to provide funding up to a maximum of $40 million to the extent HOVENSA does not have funds to meet its senior debt obligations. At December 31, the Corporation is contingently liable under letters of credit and under guarantees of the debt of other entities directly related to its business, as follows: Millions of dollars Total Letters of credit $7 Guarantees 92* $99 24