South Korea's foreign minister says it is "obvious" that North Korea sank a South Korean naval ship in March.
Yu Myung-hwan said there was enough evidence to take the issue to the United Nations.
The Cheonan warship went down near the disputed inter-Korean maritime border, with the loss of 46 sailors.
North Korea has denied any involvement. Mr Yu's remarks came as a multinational team prepares to announce the results of its investigation.
It is the clearest indication to date from South Korea that it blames Pyongyang for the sinking of the warship on 26 March.
The incident has increased tensions between the two nations.
The findings of an investigation led by experts from the US, Australia, Britain and Sweden are to be released on Thursday, with South Korea expected to blame the North.
The BBC's John Sudworth in Seoul says that for weeks South Korean media have been full of reported leaks about what that evidence will be.
An anonymous US official in Washington told the Associated Press that the investigating team would lay out evidence that the sinking of the Cheonan was the result of a North Korean torpedo attack.
Part of a torpedo propeller is said to have been discovered on the seabed and traces of explosive found on the wreck are said to match that used in a North Korean torpedo recovered a few years ago.
While the United States appears to be preparing to support the conclusions, with Secretary of State Hillary Clinton due to visit Seoul next week, China is taking a more cautious line, our correspondent says.
Its ambassador to South Korea has been quoted as saying that he does not believe that clear evidence has been discovered that proves North Korea's involvement.
Some experts have suggested that the ship could have been sunk as the result of an accidental collision with an unexploded sea mine left over from the Korean War.