Washington (AFP) – Israeli Prime Minister Benjamin Netanyahu declared Tuesday that a deal being negotiated between world powers and Iran would leave Tehran free to develop nuclear weapons.

In an impassioned address to the U.S. Congress, conducted even as Secretary of State John Kerry was in talks in Switzerland with his Iranian counterpart, Netanyahu branded Iran a global threat.

“That deal will not prevent Iran from developing nuclear weapons,” he said, placing himself in stark opposition to U.S. President Barack Obama’s policy of containing Iranian ambitions through a diplomatic accord.

“It would all but guarantee that Iran gets those weapons, lots of them,” he said.

“Because Iran’s nuclear program would be left largely intact, Iran’s breakout time would be very short.”

Around 50 Democratic members stayed away from the event, but many more lawmakers from both sides of the aisle did attend, and Netanyahu was welcomed with a standing ovation.

“I know that my speech has been the subject of much controversy. I deeply regret that some perceive my being here as political,” he said.

“That was never my intention. You want to thank you, Democrats and Republicans, for your common support for Israel year after year, decade after decade.”

“We appreciate all that President Obama has done for Israel,” he insisted, citing the close security cooperation between the countries.

But, despite his warm opening words, his speech built to a thorough denunciation of the proposed accord, citing Iranian leaders’ threats to “annihilate” Israel and “aggression” against their Middle East neighbors.

“So you see, my friends, 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.

“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.”

AFP Photo/Mandel Ngan