Israeli Prime Minister Benjamin Netanyahu warned Monday that a potential nuclear deal with Iran "could threaten the survival of Israel," as he kicked off a contentious visit to the United States meant to build the case against such an agreement. 

The centerpiece of his visit will be an address to Congress on Tuesday. But speaking first to The American Israel Public Affairs Committee in Washington, the Israeli leader underscored the dangers he said are posed by Iran, which he called the world's "foremost sponsor of state terrorism." 

"Iran envelops the entire world with its tentacles of terror," he said, displaying a map showing various connections between Iran and terror groups. He warned Iran could pursue Israel's destruction if it obtained a nuclear weapon. 

"We must not let that happen," Netanyahu said.

Both the Obama and Netanyahu administrations, as a matter of policy, agree that Iran must not be able to obtain a nuclear weapon. But the Israeli leader has concerns that the framework of the current diplomatic talks could lead to an ineffective deal. 

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His address to Congress on Tuesday has meanwhile become the source of immense tension between the two governments. The speech was arranged at the invitation of House Speaker John Boehner, but without the involvement of President Obama. Some Democrats plan to boycott that speech, and the U.S. president has no plans to meet with the prime minister -- though the White House insists this is out of a desire not to appear to be influencing upcoming Israeli elections. On Sunday, Secretary of State John Kerry said in an interview with ABC's "This Week," before he arrived in Switzerland for talks with Iran's foreign minister, that the administration did not want the event "turned into some great political football." 

But it appeared too late for that. With accusations flying on Capitol Hill, Netanyahu's visit has plunged the rocky Obama-Netanyahu relationship to perhaps its lowest point. 

Sen. John McCain, R-Ariz., told Fox News on Monday this is the "worst" he's ever seen the U.S.-Israel relationship. He claimed critics are acting "in such a hysterical fashion" because they're concerned Netanyahu will make a "compelling argument" against the pending Iran agreement. 

Netanyahu, though, stressed Monday that the alliance is "stronger than ever" despite the current disagreement, as he gently mocked the recent media coverage. 

"Never has so much been written about a speech that hasn't been given," he said. Netanyahu also said he meant no "disrespect" to Obama or his office in agreeing to address Congress. He said he "deeply" appreciates all Obama has done for Israel and did not intend to "inject Israel into the American partisan debate." 

But he said he had a "moral obligation" to speak up about the dangers Israel faces, and stressed that these dangers are, for his country, a matter of "survival." 

The prime minister's address was to be bracketed by speeches from two senior U.S. officials: U.N. Ambassador Samantha Power and National Security Adviser Susan Rice. 

Power, who spoke Monday morning, tried to ease tensions and offer assurances of the strength of the U.S.-Israel relationship. She said that partnership "transcends politics" and always will. 

She stressed that diplomacy with Iran is the "preferred route" but the U.S. will keep its security commitments. 

"The United States of America will not allow Iran to obtain a nuclear weapon, period," she said. "There will never be a sunset on America's commitment to Israel's security." 

In Washington, Netanyahu has positioned himself squarely against the Obama administration on the issue of the Iran talks. The Israeli leader is expected to press his opposition to a diplomatic accommodation of Iran's program in his speech Tuesday to Congress. 

"We are not here to offend President Obama whom we respect very much," said a Netanyahu adviser, who was not authorized to be identified. "The prime minister is here to warn, in front of any stage possible, the dangers" of the agreement that may be taking shape. 

The adviser, who spoke shortly before the delegation touched down in Washington, said Israel was well aware of the details of the emerging nuclear deal and they included Western compromises that were dangerous for Israel. Still, he tried to lower tensions by saying that Israel "does not oppose every deal" and was merely doing its best to warn the U.S. of the risks entailed in the current one. 

The Obama administration apparently is concerned about the details Netanyahu might discuss. An Associated Press journalist traveling with Kerry in Geneva tweeted Monday that Kerry said the U.S. is concerned by reports that "selective details" of the talks may be revealed. 

Netanyahu considers unacceptable any deal that does not entirely end Iran's nuclear program. But Obama is willing to leave some nuclear activity intact, backed by safeguards that Iran is not trying to develop a weapon. Iran insists its program is solely for peaceful energy and medical research. 

White House Press Secretary Josh Earnest on Monday afternoon again touted the U.S.-Israel bond, and stressed that options remain on the table -- including a military option -- if Iran does not comply with any nuclear agreement. 

He continued to give the chances for a deal a "50-50" shot, citing lingering questions over whether Iran's political leadership would sign off on one. 

The invitation to speak to Congress extended by Boehner, R-Ohio, and Netanyahu's acceptance have caused an uproar that has exposed tensions between Israel and the U.S., its most important ally. 

By consenting to speak, Netanyahu angered the White House, which was not consulted in advance, and Democrats, who were forced to choose between showing support for Israel and backing the president. 

Netanyahu's visit comes as Congress weighs legislation to trigger more sanctions against Iran if talks fail. Obama adamantly opposes that bill, but supporters could use Netanyahu's expected warnings to build their case for it. 

The Associated Press contributed to this report.