"The Prime Minister's visit to Washington is intended for one purpose -- and one purpose only. To speak up while there is still time to speak up. To speak up when there is still time to make a difference," Ambassador Ron Dermer said at an event in Florida days after House Speaker John Boehner announced that Netanyahu would address Congress in March
Netanyahu is expected to lobby Congress to approve tough new sanctions on Iran.
The scheduled appearance -- two weeks ahead of an Israeli election -- caught Obama's administration by surprise and has drawn criticism from some Democratic lawmakers
Dermer acknowledged the criticism Sunday night as he spoke at an Israel Bonds benefit event in Boca Raton, Florida
. But he said speaking out on Iran is part of Netanyahu's "sacred duty."
"There may be some people who believe that the Prime Minister of Israel should have declined an invitation to speak before the most powerful parliament in the world on an issue that concerns the future and survival of Israel. But we have learned from our history that the world becomes a more dangerous place for the Jewish people when the Jewish people are silent," he said. "That is why the Prime Minister feels the deepest moral obligation to appear before the Congress to speak about an existential issue facing the one and only Jewish state. That is not just the right of the Prime Minister of Israel. It is his most sacred duty -- to do whatever he can to prevent Iran from ever developing nuclear weapons that can be aimed at Israel."
Iran, Dermer said, remains "the world's most dangerous regime," and a nuclear deal could endanger Israel's future.
"Today, the international community stands at the precipice of forging an agreement with Iran over its nuclear program," Dormer said. "The agreement that is being discussed today is not an agreement that would dismantle Iran's nuclear weapons capability, but rather one that could leave Iran as a nuclear threshold state."
Obama has opposed upping sanctions against Iran, saying he needs more time to hash out a deal to end Iran's nuclear program and that new sanctions would put those talks at risk.
Boehner told reporters last week that he did not consult with the White House about inviting Netanyahu, saying "the Congress can make this decision on its own."
But Dermer said Sunday that the Israeli Prime MInister's visit is "not intended to wade into (the U.S.) political debate." Israel is grateful for Obama's support, he said, and support from lawmakers on both sides of the aisle.
"The Prime Minister's visit here is not intended to show any disrespect for President Obama. Israel deeply appreciates the strong support we have received from President Obama in many areas: in enhanced security cooperation, heightened intelligence sharing, generous military assistance and Iron Dome funding, and opposition to anti-Israel initiatives at the United Nations," Dermer said. "Now, I have no doubt that the Prime Minister will speak very forcefully about that strong support from President Obama when he appears before Congress."