Former U.S. ambassador to the United Nations John Bolton said Saturday that President Barack Obama's nuclear negotiations with Iran are an "unprecedented act of surrender."

Speaking at the South Carolina National Security Action Summit in West Columbia, S.C., Bolton called the deal "fundamentally flawed," reported The Hill.

"There really is no deal I'd trust Iran with," Bolton said. "It is a regime determined to have nuclear weapons, and this deal will give it to them."

The Obama administration, together with Britain, China, France, Russia and Germany, is hoping to reach a deal with Iran in which the country agrees not to pursue a nuclear weapon in exchange for the easing of sanctions. Talks between Secretary of State John Kerry and his Iranian counterpart resumed Monday in Switzerland as a March 31 preliminary agreement deadline approaches. A final deadline has been set for June 30.

A group of 47 Republican senators sent a controversial open letter to Iran's leadership last week warning that Congress can void any nuclear deal with a "stroke of the pen."

On Friday, Obama said he was "embarrassed" for the signers, calling the Republican senators' move "close to unprecedented." Many critics have suggested the open letter was an act of treason.

One of the signers, Senator Rand Paul, R-Ky., said over the weekend that he signed the letter to give Obama more leverage in the negotiation process - "because I want the president to negotiate from a position of strength which means that he needs to be telling them in Iran that 'I've got Congress to deal with,'" reported The Huffington Post

Bolton, a Republican who served under George W. Bush, defended the senators, saying they were not traitors but lawmakers who "stood up for the Constitution."

"The president coddles the Iranian ayatollah and attacks his own countrymen and our closest allies over this deal," Bolton said, reported The Hill. "The danger we hope to avoid is now imminent. This is just one example of how the president doesn't care about America's national security."

Reaching a nuclear deal with Iran would give the country a "free pass" to develop nuclear arms, Bolton said.

Evidence that Iran is close to developing a nuclear weapon is sparse, and the country insists its nuclear program is for peaceful and civilian purposes only.

Bolton encouraged American voters to make national security the central issue of the 2016 presidential election, saying Obama's policies pose the gravest threat.

"The danger we hope to avoid is now imminent. This is just one example of how the president doesn't care about America's national security," Bolton said.

"The gravest threat to our national security sits in the Oval Office," he added. "The next two years can't pass swiftly enough. For God's sake, let's not make the same mistake in 2016."

Back in 2013, Bolton issued similar warnings, calling the United States' agreement with Iran an "abject surrender," reported The Washington Times.

"In truth, an Israeli military strike is the only way to avoid Tehran's otherwise inevitable march to nuclear weapons, and the proliferation that will surely follow," he said at the time. "Making the case for Israel's exercise of its legitimate right of self-defense has therefore never been more politically important."