Israel’s former ambassador to the United States Michael Oren hit back sharply at US Secretary of State John Kerry on Friday evening, warning that his earlier comments suggesting Israel could be blamed if Congress rejects the agreement with Iran on its nuclear activity would not deter Israel.

“If American legislators reject the nuclear deal, they will do so exclusively on the basis of US interests. The threat of the secretary of state who, in the past, warned that Israel was in danger of becoming an apartheid state, cannot deter us from fulfilling our national duty to oppose this dangerous deal,” Oren, now a member of the centrist Kulanu party, said in a statement Friday.

Last year, amid a collapse of the US-brokered peace talks between Israel and the Palestinians, Kerry reportedly warned that Israel was in danger of becoming an apartheid state — a comment he later walked back.

As part of the Obama administration’s current campaign to push the Iranian deal signed last week in Vienna, Kerry told an audience at the Council of Foreign Relations in New York on Friday that should Congress vote against the agreement, “our friends in Israel could actually wind up being more isolated, and more blamed.”

Kerry also warned earlier Friday that any Israeli military action against Iran over its nuclear program would be an “enormous mistake” and would have “grave consequences for Israel and for the region.”

Oren has butted heads with the US since he published a series of essays last month criticizing the Obama administration, ahead of the release of his memoir on the Israel-US relationship, “Ally.”

In June, he penned three opinion pieces that received mixed reactions from US political figures and the Jewish community: “How Obama abandoned Israel” in the Wall Street Journal; followed by “Why Obama is wrong about Iran being ‘rational’ on nukes,” in the Los Angeles Times; and, in Foreign Policy Magazine, “How Obama Opened His Heart to the ‘Muslim World.”

Oren has said he believes “Obama is not anti-Israel” but that he has engaged in a major policy shift vis-a-vis Israel.

The former ambassador has also said the release of his book aims to enlist American Jews to fight the nuclear deal with Iran at a “critical moment” reminiscent of the lead-up to the Holocaust.

The nuclear deal signed in Vienna now goes to Congress, which has started a 60-day review of the deal and is expected to vote on it by September 17. Congress can pass a motion of disapproval, which President Barack Obama can veto. An override of the veto requires two-thirds approval in both the House and Senate.

Israel and the pro-Israel lobby AIPAC have kicked off a major lobbying campaign against the deal, with hundreds of pro-Israel activists from across the country descending on Capitol Hill next week to press members of Congress to reject the agreement.

Netanyahu earlier this week also urged US lawmakers to combat Iranian aggression by rejecting the nuclear deal.

Kerry warned Friday that it would be embarrassing to him and a blow to US credibility on the world stage if Congress rejects the deal.

Also Friday, the US secretary of state met with the leaders of the American Jewish Committee and the Conference of Presidents of Major American Jewish Organizations to discuss the deal. The meeting was held behind closed doors, and lasted for some 90 minutes, AJC spokesman Kenneth Bandler told Bloomberg. He declined to elaborate on the content on the meeting.

AP and AFP contributed to this report.