Former Democratic presidential candidate Howard Dean spoke out against the Obama administration’s nuclear negotiations with Iran at a Capitol Hill briefing hosted by a controversial Iranian dissident group on Wednesday.

Dean said the United States has not placed enough emphasis on human rights issues in its talks with Iran and has failed to protect and resettle nearly 3,000 members of the Iranian opposition group Mujahideen-e Khalq (MEK) who are living at Camp Liberty in Iraq.

"We need to stand up to the mullahs," said Dean. "These are not people we ought to be negotiating with."

He added that if Tehran walked away from a deal due to pressure over human rights issues, then the regime is "most likely going to kill the negotiations as soon as they get out of the economic problems their sanctions are causing them."

At least two MEK members were reportedly killed in a rocket attack on Camp Liberty last month. An Iranian-backed militia took credit, according to Reuters.

"We ought to sign no agreement until these 3,000 [Camp Liberty refugees] are safe," said Dean.

The briefing was hosted by the Iranian-American Community of Arkansas, a member of the Organization of Iranian-American Communities, an MEK advocacy group.

MEK lobbying groups have a history of paying high-profile political leaders like Dean to speak at events. The MEK was listed as a terrorist group by the U.S. government until 2012.

Dean is one of the few progressive leaders to publicly criticize the deal. The White House has described opposition to the nuclear talks as "a march to war."

President Barack Obama’s former national security adviser Gen. James Jones also spoke at the briefing and called on the administration to protect Camp Liberty from Iranian attacks, saying the Iranian government "doesn’t want [MEK] to leave Iraq because having them all in one place makes them very easy to target."

Jones praised the Obama administration’s efforts on the Israel-Palestinian peace process, saying that it "remains at the epicenter of what needs to be resolved" in the Middle East.

The MEK was designated a terrorist group in 1997 for attacks it carried out against Iran that led to American deaths in the 1970s.

The group has had "noncombatant" status with the U.S. since 2004. It was delisted as a terrorist group in 2012 after a high-priced lobbying campaign.