Inpex Holdings Inc. will increase spending on overseas oil and natural gas projects by as much as 50 percent a year to keep pace with soaring material and engineering costs.

Annual spending on overseas projects may rise to as much as ¥300 billion over the next three to five years, compared with a capital expenditure forecast a year ago of about ¥200 billion, Chairman Kunihiko Matsuo, 72, said in an interview Friday.

The Tokyo-based company, Japan's largest oil explorer, is developing its new overseas flagship venture, the Ichthys liquefied natural gas project in Australia, after losing an operating stake in Iran's Azadegan oil field. Benchmark LNG prices have more than doubled this decade as demand outpaced supply and a shortage of contractors delayed new production ventures.