A top U.S. official says that investigating the cause of South Korea's sunken Cheonan naval vessel must come before discussions about the resumption of the six-party nuclear talks.

U.S. Assistant Secretary of State for East Asian and Pacific Affairs Kurt Campbell made the comment to reporters at the Center for Strategic and International Studies in Washington on Thursday.

Campbell said that the primary objective of the U.S. is to work with South Korea to recover the ship and, at that point, discussions can begin about the way forward in regards to North Korea.

Campbell said Washington will do all it can to help determine the cause of the sinking.

He also said South Korea and the U.S. are in complete coordination as to the steps they will take regarding future talks with North Korea.