Oyun-Erdene was wrapping up a four-day trip to Seoul, where his delegation signed memorandums of understanding on pursuing trade deals, climate change, construction and urban development, and bilateral cultural exchange.

Another key MOU calls for the two countries to establish a ministerial-level committee on rare metal cooperation to push for joint projects, technology cooperation and personnel and information exchanges.

Rare earth minerals are essential to many high-tech manufacturing processes and are used in electric vehicles, wind turbines, portable electronics, microphones and speakers.

"Around the world, electric cars and the digital economy will be further developed, and we see Mongolia as a big player in supplying copper and rare earth materials globally to support this development," Oyun-Erdene said in an interview, speaking through an interpreter.

The prime minister, whose landlocked country lies between China and Russia, said South Korea could play a key role in the logistics for Mongolia's foreign trade.

"We see South Korea as one of our customers, and the newly signed agreement between our two countries will help Mongolia trade globally through seaports such as Busan."

This year Mongolia plans to open a delayed expansion in its Oyu Tolgoi mine, one of the world's largest known copper and gold deposits, which is slated to eventually produce more than 500,000 tonnes of copper a year.

Both Mongolia and South Korea have been caught in the rising competition between the United States and China, as well as the global fallout from Russia's war in Ukraine.

In a televised meeting with Oyun-Erdene in September, Russian President Vladimir Putin said he was discussing a major new infrastructure project to deliver gas to China via Mongolia, as Moscow looks to Beijing to replace Europe as its major gas customer.

Oyun-Erdene told Reuters that Mongolia would decide whether to approve such projects when and if China and Russia agreed on a fuel deal.

The prime minister said it would be "unethical" for Mongolia to seek benefit from the war and Russia's forced pivot to Chinese markets. Mongolia is also feeling detrimental effects from the sanctions on Russia and hopes that peace and stability are restored soon, he added.

(Reporting by Josh Smith; Editing by Simon Cameron-Moore)

By Josh Smith