WASHINGTON — A U.S. cryptocurrency expert on Thursday called for South Korea to strengthen cooperation with the United States and Japan through unilateral and multilateral sanctions to counter North Korean cryptocurrency theft, including a recent major incident involving Binance. "South Korea should also deepen joint work with the United States and Japan to put additional pressure on North Korea," said Ari Redbord, global head of policy at U.S. blockchain intelligence firm TRM Labs, in a written response to Yonhap News Agency's inquiry on South Korea's response to last week's major theft at Binance, the world's largest cryptocurrency exchange. The U.S. Federal Bureau of Investigation said North Korea was responsible for the theft of more than US$6 billion in cryptocurrency from Binance. Pyongyang, however, rejected the accusation, calling it a "grave political provocation" against the North. "Pressure means multilateral and unilateral sanctions, diplomatic pressure on North Korea and its Chinese enablers, and action against the Chinese money laundering networks Pyongyang depends on," R