WASHINGTON - (AP) -- In a direct challenge to the White House, Israeli Prime Minister Benjamin Netanyahu stood before Congress on Tuesday and bluntly warned the U.S. that an emerging nuclear agreement with Iran "paves Iran's path to the bomb." President Barack Obama pushed back sternly, saying the U.S. would never sign such a deal and Netanyahu was offering no useful alternative.
In the U.S. spotlight for a day, the Israeli leader showed no uncertainty. "This is a bad deal. It is a very bad deal. We are better off without it," he declared in an emotionally charged speech that was arranged by Republicans, aggravated his already-strained relations with Obama and gambled with the longstanding bipartisan congressional support for Israel.
Two weeks ahead of voting in his own re-election back home, Netanyahu took the podium of the U.S. House where presidents often make major addresses, contending that any nuclear deal with Iran could threaten his nation's survival.
In a tone of disbelief, he said that Iran's supreme leader, Ayatollah Khamenei, "tweets that Israel must be annihilated -- he tweets."
Republicans loudly cheered Netanyahu in the packed chamber, repeatedly standing. Democrats were more restrained, frustrated with the effort to undercut Obama's negotiations. House Minority Leader Nancy Pelosi, D-Calif., did little to hide her unease and later issued a blistering statement criticizing what she called Netanyahu's condescension.
At the White House, Obama said there was value in the current economic sanctions against Iran and also in the negotiations in Switzerland aimed at restraining Iran's nuclear ambitions.
"Sanctions alone are not sufficient," Obama said. "If Iran does not have some sense that sanctions will be removed, it will not have an interest in avoiding the path that it's currently on."
The administration says there is no deal yet, but Netanyahu insists he is privy to what is being put forth.
"If the deal now being negotiated is accepted by Iran, that deal will not prevent Iran from developing nuclear weapons. It would all but guarantee that Iran gets those weapons -- lots of them," he declared. He acknowledged that any deal would likely include strict inspections, but he said "inspectors document violations; they don't stop them."
Obama declined to meet with the leader of Israel, a key U.S. ally, during this visit. Vice President Joe Biden was on a trip to Central America and so his seat as president of the Senate was filled by Republican Orrin Hatch of Utah, the Senate president pro tempore.
As Netanyahu spoke, Secretary of State John Kerry was holding a three-hour negotiating session with Iranian Foreign Minister Mohammad Javad Zarif in the Swiss resort of Montreux in hopes of completing an international framework agreement later this month to curb Tehran's nuclear program.
According to Netanyahu, the deal on the table offers two major concessions: Iran would be left with a vast nuclear infrastructure and restrictions on Iran's nuclear program would be lifted in about a decade.
"It doesn't block Iran's path to the bomb," Netanyahu thundered. "It paves Iran's path to the bomb."
He said the U.S. and the other five nations in talks with Tehran should keep pressuring with economic sanctions because Tehran needs the deal most.
"Now, if Iran threatens to walk away from the table -- and this often happens in a Persian bazaar -- call their bluff. They'll be back, because they need the deal a lot more than you do."
More than four dozen House and Senate Democrats said in advance they would not attend the event, highly unusual given historically close ties between the two allies. Many of Netanyahu's comments were greeted by loud applause from U.S. lawmakers, but not everyone was persuaded by his rhetoric.
Pelosi issued a statement saying she was "near tears throughout the prime minister's speech -- saddened by the insult to the intelligence of the United States."
But Senate Majority Leader Mitch McConnell, R-Ky., said the Senate would debate next week on legislation that would allow a congressional vote on any deal reached with Iran. He said legislation for stiffer sanctions could well be considered.
Sen. Mark Kirk, R-Ill., who has co-authored sanctions legislation, said Netanyahu's speech would sway more lawmakers to support his bill.
"I think that's why Pelosi is crying so much on TV," Kirk said.
The legislation he has introduced with Sen. Robert Menendez, D-N.J., was approved by the Senate Banking Committee. Kirk predicted it would garner the 67 votes in the Senate that would be enough to override a presidential veto. "It really doesn't matter what the president does," he said.
Rep. Peter King, R-N.Y., called Netanyahu's speech "electrifying." Rep. Ileana Ros-Lehtinen, R-Fla., called it "phenomenal" in clearly stating "why this deal is going to be very damaging for world security, U.S. interests in Israel."
On the other side, Democrats said "alarmist" predictions by Netanyahu have been wrong before, most notably on the Iraq war.
"This is a prime minister who's never seen a war he didn't want our country to fight," said Rep. Jared Huffman, D-Calif.
Netanyahu's speech reverberated in Israel, too.
Said Isaac Herzog, who is running against Netanyahu: "The painful truth is that after the applause, Netanyahu remains alone and Israel remains isolated and the negotiations with Iran will continue without Israel. It won't change the (U.S.) government's position and will only widen the divide with our great friend and our only strategic ally."
In Tehran, spokeswoman of Iranian foreign ministry, Marzieh Afkham said Netanyahu's speech was a "deceitful show" and part of a campaign by hardliners in Tel Aviv ahead of the election in Israel.
Associated Press writers Dina Cappiello, Matthew Daly, Charles Babington, Donna Cassata, David Espo, Nedra Picker and Laurie Kellman contributed to this report.