A top U.S. diplomat has called on Southeast Asian financial institutions to remain vigilant in monitoring transactions that could assist North Korea's nuclear and missile programs.

Philip Goldberg, the U.S. coordinator for the implementation of recent U.N. sanctions on Pyongyang, made the comment on Thursday in Singapore after meeting with top financial authorities.

Goldberg said he believes there is a greater awareness among banks of their responsibilities in regards to the sanctions.

However, he acknowledged that tracking down the North Korean money trail is a difficult process, as the North is not dealing in open transactions.

Goldberg is on a four-nation Asian tour that also will take him to Thailand, South Korea and Japan.