SEOUL, July 5 (Reuters) - South Korea plans to increase the contribution of nuclear power in the country's energy mix to 30% or more by 2030 from 27% in 2021, the industry ministry said on Tuesday, pledging to resume stalled construction work on two reactors.

South Korea's new president, Yoon Suk-yeol, has rejected the idea of phasing out nuclear energy and made it a key pledge of his campaign to boost investment in the industry and revive its status as a key exporter of safe reactors.

The U-turn in Asia's fourth-largest economy towards a pro-nuclear energy policy comes after Yoon won the March presidential election by the smallest margin in South Korea's democratic history.

The previous Seoul administration sought to reduce the role of nuclear power in the wake of Japan's Fukushima disaster in 2011, which triggered a global downturn in the nuclear power industry.

The ministry said on Tuesday South Korea will resume construction work on two new reactors, Shin Hanul 3 and 4, and extend the operations of existing reactors.

While boosting the role of nuclear energy, the country plans to reduce its reliance on fossil fuel imports from 81.8% in 2021 to around 60% by 2030, the ministry said.

"As the global carbon neutrality trend continues and global energy supply chain instability increases due to the Russia-Ukraine crisis and other factors, the role of energy policy in achieving energy security and carbon neutrality goals is more important than ever," it said in a statement.

Meanwhile, the ministry will also revisit the previous administration's renewable energy goals, and decide on new targeted portions for solar and wind power.

Renewable energy's share in the country's energy mix will be "realistically adjusted to below 30%" by 2030, an industry ministry official told Reuters, compared with 6.3% last year, and the previous administration's lofty 2050 projection of 60.9-70.8%. He declined to be identified as he was not authorized to speak to media.

Coal will be "reasonably" reduced, while keeping supply-and-demand conditions in consideration, the ministry added.

South Korea is the world's fourth-largest oil importer after China, India and Japan, according to state-run Korea National Oil Corp (KNOC), while its state-run Korea Gas Corp (KOGAS) is the world's largest single corporate buyer of liquefied natural gas (LNG), according to a KOGAS spokesperson. (Reporting by Soo-hyang Choi, Joyce Lee and Byungwook Kim; Editing by Christopher Cushing and Kenneth Maxwell)