'Warmonger!' Ted Cruz heckled by peace activists outside White House
U.S. Republican presidential candidate Senator Ted Cruz shakes hands with with Code Pink peace activism group co-founder Medea Benjamin (L) after engaging in a lengthy debate on the Iran nuclear deal in Lafayette Park across from the White House in Washington July 23, 2015. REUTERS/Jim Bourg

Republican presidential contender Ted Cruz engaged antiwar activists on Thursday in a spirited debate outside the White House over the Iran nuclear deal, offering a rare moment of spontaneity in the U.S. presidential race.

A news conference organized by opponents of the Iran deal threatened to devolve into chaos as members of the antiwar group Code Pink showed up to offer a high-volume counterpoint at the event, which took place in a park across Pennsylvania Avenue from President Barack Obama's official residence.

As Cruz began to speak, Code Pink activists jumped in front of the podium with signs supporting the deal. "We want diplomacy, not war!" one shouted through a bullhorn.

"Hold on a second - you want to yell and scream? Come forward," said Cruz, who invited Code Pink leader Medea Benjamin to debate him on the merits of the deal.

For the next 20 minutes, the conservative Texas senator and the diminutive peace activist best known for getting kicked out of congressional hearings engaged in a back-and-forth over national security and diplomacy.

"The entire world is saying this is the best deal we're going to get," Benjamin said. "What makes you think as Ted Cruz you know better than all of these countries together?"

Cruz argued that Iran would use the money it earns from increased trade when sanctions are lifted to boost its military, increasing the threat to the United States and its allies.

"If the deal goes through, the Obama administration will become the world's leading state sponsor and financier of radical Islamic terrorism," he said.

As they spoke, supporters jockeyed to get their signs in front of the television cameras.

"We're all going to have peaceful conversation, but hopefully not poke people with our signs," Cruz said at one point.

Benjamin and Cruz concluded with a handshake after 20 minutes.

Afterward, Cruz continued the discussion with Code Pink activist Nate Atwell, who sported a pin-striped suit above his pink t-shirt. The two strolled through the park, surrounded by a scrum of cameras, to the occasional catcall of "Warmonger!" and "Trump for president!"

Atwell, 24, said he came away impressed with Cruz, even though he did not share his views. "He's so much smarter than he appears to be on the television," he said.