A high-ranking government official has called on the two Koreas to formally negotiate on a state-level the issue of South Korea's fertilizer aid to North Korea.

The official said on Monday that the Seoul government's position on sending fertilizer to the North is to offer the aid on a humanitarian level and to implement the plan after normal talks between South and North Korean government officials.

The official's remarks come amid reports that the United States is considering ways to exert further pressure on the communist regime, including possible economic sanctions, after Pyongyang declared last week that it possesses atomic weapons and would indefinitely boycott the six-party nuclear talks.