Seoul, South Korea - South Korea has concluded that a North Korean torpedo sank one of its warships in March, killing 46 sailors, according to government officials and domestic news reports on Tuesday. South Korean officials are preparing to announce the results of their investigation later this week.

The much anticipated finding will accuse North Korea of committing one of the worst military provocations on the Korean Peninsula since the end of the Korean War, deepening tensions between the countries. North Korea, denying involvement in the sinking, has vowed to retaliate against any attempt to link it with the March 26 explosion that broke the South Korean corvette in half near a disputed sea border. But the South has pledged "resolute measures," including economic sanctions, once the investigation is complete.

"We will blame a torpedo attack and link it to North Korea," said a government official briefed on the investigation, adding that the authorities were still fine-tuning an official announcement to be made on Thursday.

He refused to discuss forensic evidence that will be cited in the report.

In a series of closed-door briefings scheduled for today, the Foreign Ministry intends to present to Chinese, Russian, Japanese and European diplomats "scientific and objective evidence to back up the conclusion that it was a North Korean torpedo attack," said the South Korean news agency Yonhap.

The finding is hardly a surprise. In recent weeks, South Korea's defense minister has said that a torpedo attack was the likely cause of the sinking and that residue of an explosive used in torpedoes had been found in the ship's hull.

But South Korea has carefully marshaled its evidence in a multinational investigation into the sinking to try to ensure that it can rally international support for economic and diplomatic sanctions against the North.

Investigators established what they said was a critical forensic link when they matched metal pieces and traces of explosive recovered from the ship and the site where it sank with a stray North Korean torpedo secured by the South seven years ago, Yonhap and other South Korean news media outlets reported. They also said they had found a fragment believed to be part of a North Korean torpedo's propeller.

The investigators have also been scrutinizing intercepted North Korean military communications to try to link the attack to a North Korean submarine, officials here said.

South Korean officials said that if they proved that the ship was attacked by a torpedo, people would naturally believe that the attacker was the North, with its long history of military and terrorist provocations against the South.

But it remains unclear whether the forensic evidence the South has so far accumulated will be convincing enough to force China, a veto-wielding member of the U.N. Security Council and a North Korea ally, to support a statement or resolution denouncing the North.

President Lee Myung-bak of South Korea needs Chinese support. His plan to punish the North would further weaken his country's already diminished diplomatic leverage over the North Koreans because it would deepen the North's economic dependence on China at the expense of inter-Korean trade, analysts said.

Meanwhile, opposition candidates in local and provincial elections scheduled for June 2 accused Lee of whipping up anti-North Korean sentiments to win conservative votes for his party's candidates.

"The government is unable to present any factual evidence that the ship was broken in half by a torpedo," Yoo Si-min, an opposition candidate, said in a radio interview. "If they make their announcement without such evidence, they will make South Korea an international laughingstock."

Lee planned to make a speech next week to follow up on the announcement Thursday by the Defense Ministry. In recent weeks, he and other senior officials have dropped widespread hints that the North was to blame, although they have not formally accused it.

South Korean officials have suspended financing for government-level exchanges with North Korea and have asked South Korean companies not to start any new deals with the North.

Lee talked with President Barack Obama on Tuesday. The White House later said that the two leaders were "committed to follow the facts of the investigation wherever they lead." The finding of a torpedo attack would almost certainly darken the prospects for inter-Korean relations, which have deteriorated badly since Lee's inauguration in 2008. It could also block an early resumption of six-nation talks on dismantling the North's nuclear weapons programs.

South Korea has ruled out any military counterattack but is considering a drastic reduction of in inter-Korean trade, according to officials here.