JERUSALEM—Israeli Prime Minister Benjamin Netanyahu has sought to defuse tension with the US after announcing the appointment of a communications director who had previously accused Barack Obama of anti-Semitism.

Philosophy lecturer Ran Baratz was named as Netanyahu's chief spokesman last week. Israeli media immediately revealed several of Baratz's Facebook posts, including one that described President Obama's criticism of Mr Netanyahu's opposition to the Iran nuclear deal as "the modern face of anti-Semitism in Western and liberal countries".

In another post, Baratz described US Secretary of State John Kerry as having a "mental age" of no more than 12. He has also criticised Israeli President Reuven Rivlin, suggesting that he was "such a marginal figure", even Islamic State militants would not want him as a hostage.

Netanyahu has moved quickly to distance himself from the comments, ahead of his visit to the White House this week for a US-Israeli summit.

"I have just read Dr Ran Baratz's posts on the internet, including those relating to the president of the state of Israel, the president of the United States and other public figures in Israel and the United States," said Netanyahu in a statement.

"Those posts are totally unacceptable and in no way reflect my positions or the policies of the government of Israel. Dr Baratz has apologised and has asked to meet me to clarify the matter following my return to Israel."

US state department spokesman John Kirby said Baratz's Facebook posts were "troubling and offensive". Baratz's appointment has been widely criticised in Israel, and still requires Cabinet approval.