The State Department warned Monday that the future of North Korean nuclear disarmament talks depends on an investigation into the sinking of a South Korean naval ship that exploded near the border with the North last month.
Deputy Secretary of State James Steinberg's comments were a show of solidarity with South Korea, a U.S. ally that has reacted with fury and grief at what many in the South consider a North Korean attack. The investigation complicates diplomatic efforts to restart negotiations aimed at persuading the North to abandon its nuclear weapons programs.
Steinberg said that the United States wants a thorough investigation into the March 26 explosion of the Cheonan, which killed 46. In a speech at the Brookings Institution think tank, he also pledged to "follow the facts where they point."
"How we proceed is going to depend first on the clarity on the cause of the sinking of the Cheonan," Steinberg said.
North Korea must demonstrate willingness to abide by past nuclear disarmament commitments, he added, and "more broadly, (to) ending its belligerent and threatening behavior toward its neighbors."
Steinberg wouldn't discuss what specific actions the Obama administration might take should North Korea be found to have sunk the naval vessel. Investigators have reached no conclusions yet.
"We can't be indifferent to this event. This is a deep tragedy for South Korea and the people of South Korea are entitled to as full an explanation as possible as to what caused it," Steinberg said. "Until we have clarity about this, I think it's important for us to be careful about how we move forward, leaving open any of the possibilities."
Seoul has not directly blamed North Korea for the sinking, and Pyongyang has denied involvement. Suspicion, however, has focused on the North, given its history of attacks.
South Korea's defense minister said Monday that traces of an explosive chemical substance used to make torpedoes were found in the ship's wreckage.
North Korean leader Kim Jong Il has reportedly said his country is willing to return to the nuclear talks it abandoned in December 2008.
Steinberg said that China, the North's major ally and the host of the nuclear talks, has played "an important and constructive role" as diplomats discuss the Cheonan sinking.
"We very much hope that during this recent visit of Kim Jong Il to China that they had on opportunity to share with him their concerns about North Korea's behavior and to make clear that we are watching very closely to see how events unfold in connection with the Cheonan," Steinberg said.
The two Koreas remain in a state of war because their three-year conflict ended in a truce, not a peace treaty, in 1953.