North Korea has reacted sharply to a US-South Korea agreement to strengthen Washington's "extended deterrence" against Pyongyang. The North suggested countermeasures with "more powerful strength."

Kim Yo Jong, the sister of North Korean leader Kim Jong Un, released a statement via state-run media on Saturday.

The statement slammed the Washington Declaration issued after Wednesday's summit between US President Joe Biden and South Korean President Yoon Suk-yeol.

As North Korea is accelerating its missile and nuclear development, the declaration said that the US will strengthen its extended deterrence. Such deterrence refers to the US commitment to defend Seoul and other allies with all its capabilities, including nuclear weapons.

Biden and Yoon also agreed to create a framework for sharing information on nuclear weapons, and for a US nuclear ballistic missile submarine to make a port call in South Korea.

Kim Yo Jong criticized the agreement as a typical product of the two leaders' extreme anti-North Korea hostile policy.

She also denounced Biden's warning in a news conference after the summit that a nuclear attack by North Korea would mean "the end of whatever regime." She also called the president "an old man with no future."

She went on to warn that "the pipe dream of the US and South Korea will henceforth be faced with the entity of more powerful strength."