South Korea will formally blame North Korea for sinking one of its navy ships in March, killing 46 sailors, The Washington Post reported on Tuesday.
Citing unidentified U.S. and East Asian officials, the newspaper said on its Web site Seoul had reached the conclusion that North Korea was responsible for the torpedo attack after investigators from Australia, Britain, Sweden and the United States pieced together portions of the ship, Reuters reported.
The navy ship Cheonan sank on March 26 after an explosion on the vessel as it sailed in the Yellow Sea off South Korea's west coast.
The Post said the officials, who spoke on condition of anonymity because South Korea had not yet disclosed the results of the investigation, said analyses showed the torpedo was identical to a North Korean torpedo previously obtained by South Korea.
The formal accusation is expected to be announced on Thursday and South Korea will ask the U.N. Security Council to take up the matter, Post sources said.
The White House said President Barack Obama and South Korean President Lee Myong-bak spoke about the Cheonan incident by telephone Monday night but did not disclose details of the investigation.
Lee thanked Obama for U.S. help in the investigation and Obama repeated the U.S. commitment to South Korea's security, a White House statement said.
South Korean officials had made little secret of their belief that Pyongyang, which has raised concerns around the world with its nuclear tests, was behind the attack.
The report comes amid a growing chill in relations between the rival Koreas, which remain technically at war under a truce that ended fighting in the 1950-1953 Korean War.
Seoul's belief in the North's involvement in the sinking of the Cheonan has also been a source of friction between Seoul and Beijing.