With tensions high between the U.S. and Israel on the subject of an Iran deal, U.S. Secretary of State John Kerry spoke Thursday afternoon with Prime Minister Benjamin Netanyahu, telling American media shortly afterwards that he respects the Israeli leader's concerns completely.

Speaking on NBC, Kerry added that the U.S. and Israel's goal is a shared one - to stop Iran from acquiring the ability to create nuclear weaponry.

"We're having a very friendly and civil conversation about this," Kerry said. "I respect completely his deep concerns - as a prime minister of Israel should have - about the existential nature of this threat to Israel. We understand that."

On the topic of expanding sanctions on Iran, the two nations are at a disagreement, he added. According to Kerry, the U.S. wants Congress to avoid placing additional sanctions on Iran, while Israel considers such a move positively.

Reaffirming his personal commitment to the prevention of a nuclear capable Iran, Kerry added that the deal being formulated in Geneva is "failsafe."

Erdan blasts western negotiation efforts

Earlier on Thursday, the tense back and forth continued with Home Front Defense Minister Gilad Erdan issuing a sharp rebuke to Kerry's recent criticism of the Israeli government's reaction to developments concerning an Iran deal.

Addressing a conference hosted by the Institute for National Security Studies, the Likud minister said he was "shocked to hear Kerry's statement, on why [Netanyahu] is critical of the deal being developed," according to a report by NRG.

"When we are discussing a nation that wants to destroy Israel, and conditions which will allow it to do so, what can be expected of the Israeli prime minster?" Erdan asked. "That he refrain from raising his voice while the knife is being held, that he only do so when the knife is put to our throat?"

Erdan's comments came in the wake of a marked escalation in rhetoric surrounding the Geneva talks. On Tuesday, Kerry gave a Capitol Hill briefing described by Republican lawmakers as fairly anti-Israeli," while his State Department dismissed Israeli evaluations of the proposed nuclear deal with Iran as inaccurate, exaggerated and not based in reality.

Erdan sought to portray the Iranian negotiators as the hands-down winners of the recent talks on Iran's nuclear program. "Iranian Foreign Minister Zarif and his friends are walking around Geneva with huge grins on their faces [] They themselves cannot believe the ease with which they are bringing down the sanctions."

A temporary agreement, warned Erdan, will become permanent, who warned of the implications of a nuclear Iran. "Whoever is involved in this deal must realize that the moment Iran gets to the cusp of nuclear ability, the Middle East will commence on an armament race and the region's instability will increase."

Kerry to Congress: No new sanctions

Meanwhile, the U.S. Senate committee is considering new sanctions legislation, which it delayed before a round of negotiations over the weekend in Geneva that failed to reach a deal.

The P5+1 presented a unified proposal, which was not accepted by Iran during the high-level talks, U.S. officials said. Negotiations are to resume November 20 in an effort to clinch a temporary deal on halting parts of Iran's nuclear program in exchange for suspension of some sanctions.

Kerry told reporters before the hearing that the deal that fell through was only a first step and if it ultimately didn't work out, the United States "reserves the right to dial back up the sanctions."

Members of the U.S. Congress who aren't willing to negotiate, said Kerry, "ought to be clear that they, in essence, are suggesting that war is the only alternative."

White House spokesman Jay Carney said it was not the time for new sanctions. U.S. President Barack Obama is trying to resolve the standoff diplomatically, he said, because the other way of preventing Iran from acquiring a nuclear weapon is military action.

"The president won't take that off the table," Carney said. "He's very serious about the fact that the window of opportunity to pursue a diplomatic solution is open but will not stay open forever."