WASHINGTON, United States (AFP) — Israel’s Prime Minister Benjamin Netanyahu denounced President Barack Obama’s drive for a nuclear accord with Iran on Tuesday, warning Washington is paving Tehran’s path to a bomb.

After Netanyahu delivered an impassioned address to the US Congress, an exasperated Obama retorted that the Israeli leader had no plan of his own to contain the Iranian threat.

And, with US Secretary of State John Kerry in talks with his Iranian counterpart in Switzerland, the “P5+1” world powers pressed on for an accord that would limit Iran’s nuclear options while loosening economic sanctions.

Netanyahu’s party faces a close-fought Israeli parliamentary election in two weeks’ time and he has been accused of imperilling Israel’s close ties with Washington for his own political gain.

But, in a barnstorming speech to a packed joint session of Congress, he pulled no punches in his denunciation of the accord that he expects Tehran to be offered before the month is out.

“That deal will not prevent Iran from developing nuclear weapons,” he declared. “It would all but guarantee that Iran gets those weapons, lots of them.”

Obama did not watch the speech, having arranged a video conference with European leaders on the crisis in Ukraine, but afterwards he gave the Israeli leader’s argument short shrift.

“I am not focused in the politics of this. I am not focused on the theater,”Obama said. “As far as I can tell, there was nothing new.

“On the core issue, which is how to prevent Iran from obtaining a nuclear weapon which would make it far more dangerous, the prime minister did not offer any viable alternatives.”

“We don’t yet have a deal (with Iran),” Obama added. “But if we are successful then, in fact, this will be the best deal possible to prevent Iran from obtaining nuclear weapons.”

While dozens of Obama’s Democrats stayed away from the Congress address, many more lawmakers from both sides of the aisle attended and gave Netanyahu several warm standing ovations.

“I deeply regret that some perceive my being here as political. That was never my intention,” he insisted.

“We appreciate all that President Obama has done for Israel.”

But, despite his conciliatory opening words, Netanyahu’s speech built quickly into a thorough denunciation of Obama’s efforts to strike an accord with Iran.

“This deal has two major concessions. One, leaving Iran with a vast nuclear program. Two, lifting the restrictions on that program in about a decade,” he said.

“That’s why this deal is so bad. It doesn’t block Iran’s path to the bomb. It paves Iran’s path to the bomb.”

He cited the strength of Iranian-backed factions in Lebanon, Yemen, Syria and Iraq as evidence of Tehran’s regional ambitions, and recalled threats against his own people.

Thus, he said, no nuclear deal should weaken economic sanctions against Iran until its government ends its aggressive regional stance and frequent threats against Israel.

“A deal that is supposed to prevent nuclear proliferation would instead spark a nuclear arms race in the most dangerous part of the planet,” he warned.

Netanyahu received several standing ovations in the chamber and good reviews from many US foreign policy hawks, but afterwards some Democrats accused him of “fear-mongering.”

Leading House Democrat Nancy Pelosi said she had been “saddened by the insult to the intelligence of the United States.”

In Israel, the voters who will be called to give a verdict on Netanyahu’s governing coalition in two weeks were divided.

Some watching the speech in Jerusalem told AFP they had been impressed by the respect he had been accorded in the chamber, while others were concerned that he had recklessly interfered in the domestic politics of a vital ally.

Iran denounced Netanyahu’s intervention — even as Tehran’s envoys sat with Kerry in Montreux to hammer out the nuclear agreement ahead of a March 31 deadline.

Foreign ministry spokeswoman Marzieh Afkham accused Netanyahu of spreading lies about Iran’s nuclear program, which Tehran insists is peaceful.

And she dismissed the speech as repetitious, boring and a “sign of weakness.”

European Union foreign policy chief Federica Mogherini also implicitly criticized Netanyahu, warning against “spreading fears” and promising that a deal is getting close.