U.S. Secretary of State John Kerry, right, and U.S. Secretary of Defense Chuck Hagel attend their joint news conference with Japan's Foreign Minister Fumio Kishida and Defense Minister Itsunori Onodera at the Japan-U.S. Security Consultative Committee, or the so-called "2+2" meeting of foreign and defense ministers in Tokyo Oct. 3, 2013. (ISSEI KATO/AFP/Getty Images)

Rapprochement with Iran won’t come at the expense of Israel’s security or its relationship with the United States, top Obama administration officials said Thursday, but they added that it would be “diplomatic malpractice” not to explore whether Iran’s nuclear program can be defused peacefully.

The forceful defense of engagement made by Defense Secretary Chuck Hagel and Secretary of State John F. Kerry during a visit here with their Japanese counterparts was the first high-level U.S. answer to a blistering rebuke delivered Tuesday by Israeli Prime Minister Benjamin Netanyahu. The Israeli leader warned that the West is being fooled by the new, friendlier face of Iranian leadership that is being offered by President Hassan Rouhani.

“I did not interpret Prime Minister Netanyahu’s comments as suggesting that we are being played somehow for suckers,” Kerry said. “I understood it to be a warning: Don’t be played.”

Iran does not recognize Israel and in the past has said the Jewish state must be destroyed. Israel sees an Iranian nuclear weapon as an existential threat, and Netanyahu told the United Nations on Tuesday that Israel would act alone to prevent a bomb if no other nations were willing to do so.

That was a direct challenge to the Obama administration, which has repeatedly pledged to take military action against Iran if diplomatic efforts fail. Nothing about the new diplomatic effort with Iran changes that bottom line, Kerry and Hagel said.

Kerry praised Rouhani for bucking hard-liners at home to reach out and propose substantive new talks about an advanced nuclear program in his country. The United States fears the program is aimed at developing a bomb; Israel says it is certain of that intent.

Iran has pledged to bring an offer to disarmament talks later this month in Switzerland. U.S. negotiators hope the offer will include a willingness to accept limits on Iranian enrichment of uranium, the fuel that can be used either for power plants or weapons. Iran is seeking relief from crushing economic sanctions that have been imposed by the international community as its nuclear program advanced.

Iran’s new willingness to talk led President Obama to call Rouhani as the Iranian leader left the United Nations meeting in New York last week — the first such direct contact between a U.S. leader and an Iranian one since before the storming of the U.S. Embassy in Tehran in 1979.

Hagel said he understands Israel’s concern over the turnabout, but added, “I have never believed that foreign policy is a zero-sum game.”

“Engagement is not appeasement, it’s not surrender, it’s not negotiation,” Hagel said. “Aren’t we wiser if we can find ways to resolve disputes, recognizing the danger, being very clear-eyed and keeping the strongest military in the world?”

Netanyahu used his U.N. address on Tuesday to pick apart the Iranian leader’s overtures, calling Rouhani a “wolf in sheep’s clothing.” Rouhani’s effort, Netanyahu said, was nothing but a “charm offensive” to get the West to ease sanctions.

In an interview with NBC on Wednesday, Netanyahu went further. Iran’s supreme leader, Ayatollah Ali Khamenei, heads a “cult” bent on Israel’s destruction, Netanyahu said, and Khamenei, not Rouhani, will decide the country’s nuclear direction.

Kerry said that Iran’s assurances — that it seeks only peaceful nuclear energy, not a weapon — will be put to the test at the negotiating table.

“I can assure the prime minister, as I would assure all the people of the world, and particularly Iranians, there is nothing here that is going to be taken at face value,” the chief U.S. diplomat said Thursday.

“We have an obligation,” Kerry said. “It would be diplomatic malpractice of the worst order not to examine every possibility . . . before you ask people to take military action or do what you have to do.”

In Washington on Thursday, the leader of the Obama administration’s Iran negotiating team was pressed at a Senate hearing to clarify what kinds of concessions the United States might be willing to offer Tehran officials at the talks in Geneva.

“I understand the need to test the diplomatic possibility, but by the same token, I get concerned when I hear about easing of sanctions,” Sen. Robert Menendez (D-N.J.), chairman of the Senate Foreign Relations Committee, told Wendy Sherman, the State Department’s undersecretary for political affairs.

Sherman said the Geneva talks, which are scheduled to begin Oct. 15, would focus on “confidence building,” including “some early test” to gauge Iran’s sincerity. But, she insisted, “the fundamental, large sanctions that we have in place should not disappear unless all our concerns are addressed by the Iranians.”

Joby Warrick in Washington contributed to this report.