He has accused Barack Obama of anti-Semitism, suggested his own country's president was not important enough to assassinate and described U.S. Secretary of State John Kerry as having the mental abilities of a 12-year-old.

Ran Baratz's Facebook and web page barbs might have remained forever on the margins of social media, save for one thing: the appointment of the 42-year-old philosophy lecturer as Israeli Prime Minister Benjamin Netanyahu's new communications director.

As head of public diplomacy and media, Baratz, who was named to the post on Wednesday, will be tasked with improving Israel's reputation in the world.

But days before Netanyahu embarks on a visit to the White House, an effort to mend fences after fierce feuding over the Iran nuclear deal that Israel opposes, the timing of the decision to give Baratz the job raised questions.

Within hours of his appointment, Israeli media outlets found a clutch of cuttings, headline-grabbing quotes on Facebook and articles he had penned on news web sites. Netanyahu's staff, it appeared, may not have checked.

"Prime Minister Benjamin Netanyahu was unaware of the things Ran Baratz wrote and sees them as inappropriate remarks," the Israeli leader's office said in a statement on Thursday.

"Baratz made clear to the prime minister that the public role requires he conduct himself in a statesman-like and reserved manner, which he was not obligated to do as a private person on Facebook."

In a Facebook entry last March, Baratz said Obama's response to a speech by Netanyahu to the U.S. Congress, during which he criticized the emerging Iran deal, "was what modern anti-Semitism looks like in Western and liberal countries".

The White House was not immediately available for comment. Obama said at the time that no one could dispute that Iran had repeatedly "engaged in the most venomous of anti-Semitic statements". But, the president said, Netanyahu offered no viable alternatives "to the core issue, which is how do we prevent Iran from obtaining a nuclear weapon".

In October last year, Baratz took aim at Kerry in an article on Mida, which bills itself as a "news and intellectual website" dedicated to providing information and views that are not prevalent in other Israeli media.

Baratz termed as "comical" remarks Kerry made on the occasion of a Muslim holiday, when he said Middle East leaders had told him feelings stirred by the Israeli-Palestinian conflict were a factor in Islamic State recruitment.

"This is the time, then," Baratz wrote, "to wish the secretary of state success and count down two years on the calendar with the hope that someone in the State Department will then wake up and begin to see the world through the eyes of a man with a mental age above 12."

The U.S. State Department did not immediately comment on Thursday when asked about the remarks.

CRITICISM OF ISRAELI PRESIDENT

Sniping at Israel's head of state, Baratz commented on Facebook last week about photos showing President Reuven Rivlin -- whose post is largely ceremonial -- sitting in economy class on a flight back from an official visit to the Czech Republic.

"It mainly shows him to be such a marginal figure that there is no concern for his safety. I think he could be sent in a para-glider to the Syrian Golan [Heights] controlled by ISIS. They'll return him the next day with a request for negotiating their return to Iraq, if only we take him back," Baratz wrote.

Baratz posted a separate remark on Facebook under a screen grab of a TV interview with Daniella Weiss, a Jewish settler leader. The frozen frame carried a subtitle, which read: "He is not important enough to kill", a reference to Rivlin.

Baratz appeared to concur, writing: "I said that way before she did, but it's good when practical people confirm the observations of theoreticians". He was quoted by Israel's Channel Two television as saying his statement was satirical.

Rivlin's office publicly demanded to know whether Netanyahu was aware of Baratz's comments when he appointed him.

"The remarks are particularly serious in light of the fact that this is a senior civil servant who is supposed to serve in a representative capacity and reflect the positions of the State of Israel at home and abroad," the president's office said.

"It is also troubling that the candidate cast his comments as mere 'satirical statements,' and this at a time when Israel is waging a real war through social media based on an understanding of the power of such posts, and the short distance between them and legitimizing an act."

A phone call and text message to Baratz from Reuters, requesting comment, went unanswered.

Baratz, who lives in a West Bank settlement, also expressed support in 2004 for the construction of a third Jewish temple on what is now the Aqsa mosque compound in Jerusalem, where two destroyed biblical temples once stood.

Muslim allegations, denied by Israel, that Netanyahu intends to change a long-standing status quo under which Jewish prayer is banned at the sensitive site, have helped fuel a wave of Palestinian stabbing and shooting attacks.

Eleven Israelis have been killed. At least 68 Palestinians have been shot dead by Israeli forces, including 41 who Israel says were attackers. Many were teenagers.

"The desire to build the third temple is worthy, Jewish and Zionist to the first degree," Baratz wrote on the NRG news website 11 years ago, acknowledging such aspirations were harbored by fringe elements in Israeli society.

But he added: "I wish a way could be found to build it."