SEOUL: South Korea's leader warned Thursday the peninsula could slide back into a "state of crisis" if Pyongyang follows through on threats to resume testing long-range missiles.

Pyongyang conducted an unprecedented seven weapons tests in January, including of its most powerful missile since 2017 when leader Kim Jong Un baited then-US president Donald Trump with a spate of provocative launches.

High profile negotiations between Trump and Kim followed, but collapsed in 2019 and have languished as Pyongyang has doubled down on military development, warning last month that it could abandon a self-imposed moratorium on long-range missile and nuclear weapons tests.

In a written interview with international press agencies including AFP, President Moon Jae-in said that any move by North Korea to restart long-range missile tests would wipe out years of effort and peace talks.

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"If North Korea's series of missile launches goes as far as scrapping a moratorium on long-range missile tests, the Korean Peninsula may instantly fall back into the state of crisis we faced five years ago," he said.

Moon, who repeatedly pursued peace talks with the North during his five-year term, is set to leave office in May. South Korea only permits presidents to serve a single term in power.

The country will elect his successor on March 9.

Despite the lack of progress in nuclear talks, "necessary communication" between Moon and Kim has continued, the South Korean president said.

The demise of the Trump-Kim talks without a deal was "very regrettable", he added, saying that the two sides should have sought a more incremental approach to making a deal.

"It would have been best if a 'big deal' had been reached... If that was too hard, however, I think a 'small deal' should have been sought to take a phased approach."

Although Trump's successor US President Joe Biden has pursued a more muted approach to North Korean diplomacy, Moon said he expected that another summit between the US leader and Kim would take place "eventually".

"It is just a matter of time," he said.