WASHINGTON — Prime Minister Benjamin Netanyahu of Israel used one of the most prominent platforms in the world on Tuesday to warn against what he considers an ill-advised nuclear deal being negotiated with Iran, putting a cap on a drama that has roiled Israeli-American relations for weeks.
In an implicit challenge to President Barack Obama, Netanyahu told a joint meeting of Congress that Iran’s “tentacles of terror” were already clutching Israel and that failing to stop Tehran from obtaining nuclear weapons “could well threaten the survival of my country.” The deal Obama seeks will not prevent a nuclear-armed Iran, he said, but “will all but guarantee” it.
“We must all stand together to stop Iran’s march of conquest, subjugation and terror,” Netanyahu told the lawmakers, who responded with repeated standing ovations.
‘‘The greatest danger facing our world is the marriage of militant Islam with nuclear weapons,’’ he said in remarks before a packed House chamber. The US plan “doesn’t block Iran’s path to the bomb, it paves Iran’s path to the bomb,” Netanyahu said.
Netanyahu pushed for current restrictions on Iran to remain in place for “as long as it continues its aggression in the region and in the world.”
“If Iran wants to be treated like a normal country, let it act like a normal country,” he said.
Netanyahu also listed parameters for lifting restrictions on the country: the restrictions should only be lifted if Iran stops its aggression in the Middle East and its support of terrorism, and stops threatening to “annihilate Israel.”
‘‘Iran has proven time and again that it cannot be trusted,’’ no matter what it says about permitting verification of the terms of any accord designed to prevent it from getting such weapons, he said.
Netanyahu’s address, by far the most anticipated speech to Congress by a foreign leader in many years, has generated resentment and reinforcement from different quarters while driving a partisan wedge between Democrats and Republicans. While he was escorted to the rostrum by a bipartisan delegation of lawmakers and greeted with raucous enthusiasm, especially by Republicans, more than 50 Democrats skipped the event.
Netanyahu tried to defuse some of the political edge that preceded his arrival by praising Obama for all he has done to support Israel. Netanyahu cited several instances when he called the president for help, such as seeking more missile interceptors during Israel’s military operations against Hamas. “I will always be grateful to President Obama for that support,” Netanyahu told lawmakers.
And he repeated a comment he made elsewhere Monday lamenting the furor that surrounded his visit. “I deeply regret that some perceive my being here as political,” he said. “That was never my intention. I want to thank you Democrats and Republicans for your common support for Israel, year after year, decade after decade.”
But he argued that Iran remains as radical and untrustworthy as ever, even though it and the United States are effectively on the same side in battling the Islamic State, also known as ISIS. “This regime will always be an enemy of America,” Netanyahu said. “Don’t be fooled. The battle between Iran and ISIS doesn’t turn Iran into a friend of America. Iran and ISIS are competing for the crown of militant Islam.”
Sitting in the packed gallery of the House chamber were Elie Wiesel, the Holocaust survivor and Nobel peace laureate; Sheldon Adelson, the Republican casino magnate and one of Netanyahu’s prime backers; and Newt Gingrich, the former speaker of the House. Vice President Joe Biden was out of the country, so standing next to Speaker John A. Boehner behind the Israeli prime minister was Sen. Orrin G. Hatch, R-Utah, who serves as president pro tempore of the Senate.
For Netanyahu, the stakes could hardly be higher. Coming just two weeks before Israeli elections, the speech offered an opportunity to build support at home for another term while rallying opposition abroad to a diplomatic accord that he sees as a threat to his country’s security.
Before the address, Abraham H. Foxman, national director of the Anti-Defamation League, predicted that it would be “the most important speech of his political life.”
For Obama, however, it was an extra complication as he seeks to draw Iran into a pact by late March, a complication he worries may embolden lawmakers into intervening.
“I’m less concerned, frankly, with Prime Minister Netanyahu’s commentary than I am with Congress taking actions that might undermine the talks before they’re complete,” he told Reuters on Monday.
In a bit of counterprogramming, the White House announced on Tuesday morning that at 11:30 a.m., around the time when Netanyahu may be wrapping up his speech, Obama was to hold a conference call with European leaders.
At the heart of the dispute between Obama and Netanyahu is a debate over the best way to curb Iran’s nuclear program. The United States, along with European allies, Russia and China, has been negotiating a potential deal in which Iran for at least 10 years would restrict the number of centrifuges it has for enriching uranium and open its program to international inspection.
The goal would be to limit Iran’s capacity so that it would take at least a year to build a nuclear weapon should it choose to violate or break the agreement. In theory, that would give the West enough time to respond. In exchange, international sanctions that have hampered Iran’s economy would be eased.
Netanyahu argues that Iran cannot be trusted given its history of cheating and hostile statements about Israel. The deal contemplated by the American-led negotiations would give away far too much, he contends. Instead, Netanyahu and other critics have advocated tightening sanctions and demanding that Iran give up all uranium enrichment.
The speech came even as Secretary of State John Kerry and Mohammad Javad Zarif, the Iranian foreign minister, continued their talks in Switzerland. In comments published Wednesday in the Iranian news media, Zarif bluntly rejected the conditions Obama outlined.
“Iran will not accept excessive and illogical demands,” Zarif was quoted as saying. “It is clear that Obama’s comments are meant to win the U.S. public opinion and counter the propaganda campaign by the Israeli prime minister.”
But in separate if sparse public comments in Montreux, Switzerland, Zarif was more conciliatory. “We’re trying, we’re trying,” he responded to a shouted question about how the negotiations were going.
Obama and his team said they shared Netanyahu’s concerns, but considered his approach unrealistic.
Simply insisting that Iran forgo enrichment altogether “is not a viable negotiating position,” Susan E. Rice, the president’s national security adviser, told the AIPAC conference Monday evening. And military strikes often favored by hawks would only temporarily set back Iran’s program, she said.
“We cannot let a totally unachievable ideal stand in the way of a good deal,” she said.
Rice vowed to hold out for a truly verifiable pact. “Our approach is distrust and verify,” she said, in a twist on a phrase made famous by President Ronald Reagan during negotiations with the Soviet Union. And she reassured Israel of Obama’s support. “We have Israel’s back, come hell or high water,” she said.
Netanyahu’s speech divided American lawmakers. Speaker John A. Boehner invited the Israeli leader without consulting the White House, seeing Netanyahu as a forceful voice challenging Obama’s foreign policy.
“This is an important message at an important time, and the prime minister is the perfect person to deliver it,” Boehner said in a video previewing the event released Tuesday.
Democrats bristled at what they saw as a partisan maneuver, and at least 55 House and Senate Democrats planned to skip the address, according to the newspaper The Hill.
Few congressional appearances by foreign leaders have generated such controversy. Netanyahu has addressed Congress twice before, in 1996 and 2011, without such a ruckus, and his speech Tuesday will be the eighth time an Israeli leader has spoken to the House and Senate together.
The only other foreign leader to have spoken to Congress three times was Winston Churchill, the British prime minister during and after World War II. In honor of that, Boehner plans to present Netanyahu with a bust of Churchill.
The flap has raised Netanyahu’s profile in the United States, but he remains a polarizing figure. Early last month, Gallup, the survey firm, found that 45 percent of Americans have a positive view of him, a 10-point jump since a similar poll in 2012, compared with 24 percent who view him unfavorably. But the views broke down sharply along party lines, with Republicans favoring Netanyahu three to one and Democrats evenly split.
In a separate poll by The Wall Street Journal and NBC News late last month, 48 percent of voters disapproved of inviting Netanyahu to address Congress without checking with the White House first, compared with 30 percent who approved.
The speech became a hot ticket. Boehner’s office reported that demand for seats in the galley were the highest since he became speaker in 2011. Interest was so overwhelming that both the House and Senate set up alternative viewing locations. Among the guests invited by Boehner was Elie Wiesel, the Holocaust survivor and Nobel Peace Prize recipient.
One person not clamoring to see the address, either in person or on television, will be Obama. Josh Earnest, the White House press secretary, said Monday, “I doubt that he will spend his whole time watching the speech.”