South Korea suspended its third attempt to send a satellite into orbit by at least three days Friday, after a helium leak was detected in the rocket just hours before scheduled launch time.

With only a five-day launch window that ends October 30, any further delay could result in a much lengthier postponement, officials at the Naro Space Centre told reporters.

After two previous failures in 2009 and 2010, the current launch is considered critical for South Korea's efforts to join an elite space club that includes Asian powers China, Japan and India.

The 140-tonne Korea Space Launch Vehicle (KSLV-I) had been scheduled to blast off from the Naro site on the south coast on Friday afternoon.

But Deputy Science Minister Cho Yul-Lae said a helium leak in the rocket's Russian-built first stage would require the carrier to be removed from the launch pad and returned to the assembly facility.

"We will set another launch date. But since we have to bring the rocket down, it will be delayed at least three days," Cho said, adding that engineers were investigating the precise cause of the problem.

"We may not be able to launch during this window, in which case we will have to shut it down and fix a new window," Cho said, without offering a possible alternative timeframe.

As with the two previous failed attempts, the KSLV-1 has a first stage manufactured by Russia, combined with a solid-fuelled second stage built by South Korea.

In 2009 the rocket achieved orbit but faulty release mechanisms on the second stage prevented proper deployment of the satellite.

A second effort in 2010 saw the rocket explode two minutes into its flight, with both Russia and South Korea pointing the finger of blame at each other.

Success this time around will mean a huge boost for South Korea -- a late entrant into the high-cost world of space technology and exploration, desperate to get its commercial launch programme up and running.

Seoul's space ambitions were restricted for many years by its main military ally the United States, which feared that a robust missile or rocket programme would accelerate a regional arms race, particularly with North Korea.

South Korea's space budget for 2012 is around $200 million, according to the Science Ministry -- a paltry sum compared to the billions being pumped in by the governments in Beijing, Tokyo and New Delhi.

In a recent paper for the Council on Foreign Relations, James Moltz, a professor at the US Naval Postgraduate School, said South Korea had little option but to pursue an expensive catch-up strategy.

"As a middle-sized power, Seoul has to invest a higher percent of its resources into space activity if it hopes to develop a sustainable niche position among Asia's larger and more established space powers, which are decades ahead of it," Moltz said.

Japan and China both achieved their first satellite launches back in 1970, and India made its breakthrough in 1980. But the lack of US support contributed to South Korea, Asia's fourth largest economy, lagging behind.

However, soon after joining the Missile Technology Control Regime in 2001, South Korea made Russia its go-to space partner -- a relationship that has been through a number of rocky patches.

Whatever the outcome this time, South Korea insists it remains committed to developing a totally indigenous three-stage, liquid-fuelled rocket capable of carrying a 1.5-tonne payload into orbit by 2021.

"Regardless of whether the third launch is a success or not, the project to develop a Korean launch vehicle will pick up greater speed and momentum," Science Minister Lee Ju-Ho told journalists this week.

"After that, we will actively develop and expand our presence in the global market for commercial launch vehicles so that we will be able to win orders from abroad to manufacture satellites and launch them with our own rockets," Lee said.