The U.S. said on Monday that the sinking of a South Korean warship blamed on the Democratic People's Republic of Korea (DPRK) is not an act of international terrorism and therefore won't put it back on the U.S. state sponsors of terrorism list.

"It is our judgment that the sinking of the Cheonan is not an act of international terrorism and by itself would not trigger placing North Korea on the U.S. state sponsors of terrorism list," said State Department spokesman Philip Crowley.

It was "a provocative action but one taken by the military of a state against the military of another state," Crowley said. "That in our view does not constitute an act of international terrorism. "

However he warned the U.S. will not hesitate to take action if it thinks actions of DPRK demonstrates consistent support for international terrorism.

The South Korean naval vessel "Cheonan," with 104 crew members onboard, sank into waters off the west coast of Korean Peninsula on March 26, leaving 46 sailors dead.

A South Korean investigation results, issued on May 20, concluded the warship was sunk by a torpedo of DPRK which firmly denied the allegation.

South Korea referred its investigation results to the United Nations Security Council on June 4, seeking condemnation on DPRK from the international organization.

The U.S. removed DPRK from the "state sponsors of terrorism" list in 2008, in an effort to get DPRK dismantle its nuclear program.