CHANGWON, South Korea, April 15 (Reuters) - South Korea's Hanwha Aerospace plans to invest about 40 billion won ($28.91 million) by 2025 in a new aircraft engine factory, as it seeks to eventually develop domestically made engines for fighter jets such as South Korea's KF-21s.

The country's largest defence company by revenue said in a statement it aims to develop a 15,000-pound-force turbo-fan engine by the mid-to-late 2030s.

The announcement comes after South Korea's government last year designated advanced aircraft engines among 30 technologies deemed investment targets as part of a 15-year plan to enhance home-grown defence capabilities.

Only six countries have indigenous engine technology that has entered into service in aircraft - the United States, Britain, France, Russia, Ukraine and China.

Hanwha currently makes parts for and assembles aircraft engines under licence from global firms such as GE and Pratt & Whitney of the United States, and France's Safran. The South Korean company also makes its own engines for ships and missiles, but it wants to do more, executives said.

"We will decide in the next few weeks how much of the project we will develop domestically and how much with foreign cooperation, but we hope to do as much as possible with domestic capabilities," Kwangmin Lee, head of aero systems at Hanwha Aerospace, told reporters at the company's manufacturing base in Changwon on the southern end of the Korean Peninsula.

Hanwha Aerospace, which originally started out as a maker of aircraft parts, now has a much larger land defence business with more than 50% share of the global market for howitzer exports, according to data by NH Investment & securities, and an order backlog of 28.3 trillion won as of end-2023.

The land defence business sells arms such as K9 howitzers, Chunmoo rocket launchers and Redback infantry fighting vehicles, and accounted for 44% of its 9.36 trillion won in 2023 sales after demand for such weapons spiked following Russia's invasion of Ukraine.

The company's aerospace business including engine assembly and parts manufacture contributed only 17% of sales last year, but Hanwha wants to expand the business long-term in order to stabilise revenue streams during peacetime as well as in war.

Hanwha announced earlier this month the spinoff of its semiconductor equipment and video surveillance businesses, carving out units that contributed about 16% to revenue to focus on its defence and aerospace businesses. ($1 = 1,383.4500 won) (Reporting by Joyce Lee Editing by Ed Davies)