North Korea seems ready for its seventh nuclear test, an official of South Korea's presidential office said Friday.

Before conducting such a test, Pyongyang may test-fire more missiles of several types, the official added, although the North has carried out missile launches 15 times since January, including the test-firing of three short-range ballistic missiles on Thursday.

In April 2018, North Korea declared it would discontinue nuclear tests. But there are signs the country is restoring underground tunnels at its nuclear test site, South Korea's defense ministry has said.

Speculation of a possible nuclear test by the North comes as U.S. President Joe Biden is scheduled to visit South Korea from May 20 and hold talks with new South Korean President Yoon Suk Yeol.

The launch of the short-range ballistic missiles on Thursday came days after the inauguration of Yoon, who has indicated he will take a hard-line stance with Pyongyang.

South Korean Foreign Minister Park Jin said the same day the government plans to draw up plans to cope with North Korea's threats ahead of the meeting between Yoon and Biden.

On Friday, Park and U.S. Secretary of State Antony Blinken held a virtual meeting and strongly condemned the North's recent provocations including the ballistic missile firing, South Korea's Foreign Ministry said.

While Park and Blinken agreed to strengthen cooperation in responding to the North's threats, they reiterated that South Korea and the United States are open to dialogue with Pyongyang, vowing to resume negotiations with the North for denuclearization, the ministry said.

They also expressed concerns over the breakout of COVID-19 in North Korea, agreeing to continue discussions to seek ways to offer humanitarian aid to the country while cooperating with other nations.

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