Jeering comments attributed to Israel's Defense Minister Moshe Ya'alon about Secretary of State John Kerry's efforts to broker a peace between Israel and Palestinians angered U.S. officials Tuesday.
Israel's Yediot Aharonot newspaper reported on Tuesday that Ya'alon had made the comments in private conversations between Israeli and American officials.
The paper claimed Ya'alon had expressed hope that John Kerry would win the Nobel Peace Prize, so that he might focus his energies elsewhere.
"Kerry - who arrived here determined, and who operates from an incomprehensible obsession and a sense of messianism - can't teach me anything about the conflict with the Palestinians," he was reported as saying.
White House spokesman Jay Carney labelled the comments "offensive and inappropriate".
But at a news conference in Kuwait, Mr Kerry said he would not allow "one set of comments to undermine peace efforts".
According to the Haaretz newspaper, he said: "I will work undeterred ... after five months of negotiations, I believe strongly in the prospects for peace and I know the status quo is not sustainable.
"We've always known that as we approach the time for these difficult choices, it's going to be difficult."
Mr Ya'alon's office issued an apology on Tuesday evening following a long meeting with Israel's Prime Minister Benjamin Netanyahu.
"The defence minister did not intend to insult the secretary and he apologises if the secretary was hurt by the remarks attributed to the defence minister," the statement read.
The statement was issued after a senior US official called on Mr Netanyahu to publicly denounce Mr Ya'alon's remarks, after he was perceived to have offered too soft a rebuke in the Israeli parliament earlier in the day.
Speaking in the Knesset, Mr Netanyahu had appeared to criticise the wisdom of singling out Mr Kerry individually, but not question the sentiment with regards to the US approach to negotiations.
"Even when we have disagreements with the United States, it is about the matter at hand and not about the person," Mr Netanyahu had said.
The diplomatic spat comes amid Mr Kerry's efforts to revive the faltering peace process and push for the establishment of a two-state solution.
The parties were brought back round the negotiating table in August and since then, Mr Kerry has made more than 10 visits to the region.
The current negotiating phase has a deadline on April 29, by which time Mr Kerry hopes both sides will have arrived at a framework agreement that could pave the way for a final deal on borders, refugees, natural resources and the status of Jerusalem.
But the comments by Mr Ya'alon have stoked already existing tensions between the Obama administration and the government of Benjamin Netanyahu.
Israel was stinging in its opposition to the US-backed deal with Iran, that aims to see parts of the country's civil nuclear programme rolled back and made more transparent in return for sanctions relief.
The US administration also slammed last week's Israeli government announcement of 1,800 new permissions for settlement construction in the West Bank as "illegitimate".
Speaking at the funeral of former Prime Minister Ariel Sharon on Monday, US Vice President Joe Biden insisted, despite some disagreements over specific policies, that American support for Israel was unwavering.
However, when speaking at the same service, Mr Netanyahu made specific reference to Mr Sharon's ability not to be pushed around by the US.
"He understood the importance of our relationship with the United States, but also knew how to stand for Israel's rights," he said during his eulogy.
(c) Sky News 2014
Original headline: John Kerry 'Undeterred' By Messiah Jibe
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