South Korea's foreign minister has resigned after an internal government row over foreign policy and US ties.
Yoon left after less than a year in the post
Yoon Young-kwan left after his officials reportedly criticised presidential advisers, who advocate an independent line from its key ally.
Press reports talk of disputes over US military bases and troops for Iraq.
President Roh Moo-hyun's advisers also favour a softer line on North Korea, which the US branded part of an "axis of evil" for its nuclear ambitions.
President Roh has accused civil servants of making derogatory remarks and leaking documents. He said he expected those who opposed his policies to be replaced.
The BBC's Seoul correspondent, Charles Scanlon, reports that President Roh's is the most left-leaning administration in South Korean history and this has led to strains with Washington.
The focus of attention has been the president's National Security Council which has been dismissed by some diplomats as young and amateurish.
Roh is taking South Korea in a more independent direction
The president's personal secretary, Jeong Chan-yong, said the foreign minister had taken responsibility for failing to implement presidential policy.
"Some foreign ministry staff were unable to shed the past foreign policy and failed to adequately understand the basic spirit of the new independent foreign policy," he told reporters.
Yoon Young-kwan's successor has not been appointed.
Our correspondent notes that Mr Yoon is a respected academic with no political background who was brought in at the beginning of the Roh administration last year.
He leaves office at a crucial moment, with regional powers and the US trying to find common ground over North Korea's development of nuclear weapons.
Mr Yoon had been credited by some with stabilising President Roh's ties with the US after he came to office.
His departure may bode ill for relations, Lee Jung-hoon, professor of international studies at Yonsei University, told Reuters news agency.