'Obvious' North Korea Sank South Korean Ship

SEOUL, South Korea, May 19, 2010— -- A North Korean torpedo was responsible for the March 26 sinking of a South Korean navy ship and the deaths of 46 sailors aboard, South Korean officials said.

Foreign Minister Yu Myung-hwan said today it was "obvious" that the North Koreans sank the Cheonan warship as it sailed near the disputed water between the two Koreas.

Officials in Seoul and Washington told ABC News that the South Korean President Lee Myung-Bak is preparing a statement for early next week that will officially blame the North and inevitably ratchet up tensions in the region.

Until now, South Korea has been careful about apportioning blame to the North without substantial evidence. Pyongyang has repeatedly denied any involvement in the sinking.

The smoking gun is a propeller that presumably powered the torpedo which a pair of South Korean fishing boats found at the bottom of the ocean last weekend. The propeller itself was in a "relatively fine condition," reported Chosun Ilbo, South Korea's largest daily newspaper.

A team of investigators from Australia, Britain, Sweden, and the United States have concluded after deciphering the serial number engraved on the propeller that the font and the engraving technique is in North Korean style.

The team has been analyzing the recovered parts of the wrecked Cheonan navy vessel at Pyongtaek port, 42 miles southwest of Seoul. They are to submit an official report on Thursday.

Also expected to be included in this report is the analysis of traces of explosives recovered from the damaged vessel and pieces of the suspected torpedo.

The South Korean press has been reporting for the past few weeks that the traces of explosives have an identical chemical make-up to the substances found in a stray North Korean torpedo which the South seized in 2003.

"The whole thing is like James Bond," said one U.S. official who confirmed to ABC News that the U.S. has a picture of the pieces from the North Korean torpedo recovered from the bottom of the ocean.

President Lee and U.S. President Barack Obama agreed during a 25-minute telephone conversation Tuesday that both countries will work to impose stronger sanctions against North Korea immediately after the official announcement is made. Japanese Foreign Minister Katsuya Okada told his South Korean counterpart on Monday that Japan is also on board to pressure North Korea.

Heightened Tensions

That leaves China, the last remaining ally of the communist North, in an uncomfortable position. The South Korean government has expressed disappointment with Beijing for inviting North Korean leader Kim Jong Il earlier this month when the South was still mourning the death of the young sailors.

The report and accusation is expected to heighten tensions in the region, one of the world's most heavily militarized borders. Officials in Seoul and Washington are reportedly considering an option to launch joint naval exercises in the area on a regular basis involving submarines.

ABC News' Martha Raddatz from Washington, D.C., contributed to this report.