SEOUL, Aug 24 (Reuters) - South Korea's new envoy on North Korean human rights called on Wednesday for diplomatic pressure to persuade Beijing against deporting defectors from North Korea.

The number of defectors plunged after the border between China and North Korea was closed in early 2020 to stop the spread of COVID-19, but once the border is reopened the numbers are expected to rise, said Lee Shin-wha, South Korea's ambassador for international cooperation on North Korean human rights.

U.N. experts have for years criticised China for sending back North Korean defectors, whom it regards as illegal migrants who flee their country for economic reasons.

Describing China as "a responsible member of the international community with power", Lee said "quiet diplomacy" might be needed to convince Beijing to adhere to the principle of non-refoulement, which obliges host countries to refrain from returning asylum seekers or refugees to a place where their life or liberty would be at risk.

"If the border reopens, there might be many refugees facing forceful repatriation, and that has to be prevented," she told a news conference in Seoul.

Lee, who teaches international relations at Korea University in Seoul, was appointed last month after President Yoon Suk-yeol took office in May. Yoon pledged to promote the human rights situation in the North.

The position had been vacant for five years, while Yoon's liberal predecessor tried to improve relations with Pyongyang, which regards Seoul's criticism of its rights record as hostile.

Earlier this month, a North Korean state radio station described Yoon as malicious and confrontational.

Seoul reported defectors arriving in South Korea had hit an all time low during the pandemic. North Korea lifted some restrictions on mandatory mask wearing and social distancing - except in border areas - after declaring victory over COVID-19 this month.