Sen. Rand Paul’s (R., Ky.) greatest vulnerabilities in the early GOP primaries are his positions on Iran and Israel, according to a private poll commissioned by a group called the Foundation for a Secure and Prosperous America.

The Republican PAC, which launched a $1 million ad campaign highlighting Paul’s foreign policy positions this week, conducted the polls of likely Iowa and South Carolina GOP primary voters in February.

While respondents were surveyed on a number of Paul’s potential weaknesses, including his association with conspiracy-minded radio host Alex Jones and opposition to mandatory minimum prison sentences, the polls indicate that Paul’s comments on Iranian nuclear weapons and aid to Israel are his biggest liability with Republicans.

Seventy-seven percent of South Carolina respondents and 76 percent of Iowa respondents said they were less likely to vote for Paul after hearing that he supported cutting military aid to Israel. When told, "Rand Paul has said that he thinks Iran having nuclear weapons in not a threat to the United States or Israel," 77 percent of South Carolina respondents said they were less likely to support him. Seventy-two percent of Iowa respondents said the same.

The polls also found growing concerns about national security in general. In South Carolina, a plurality of likely GOP voters said "Terrorism/ISIS" was the most important issue facing America, followed by the economy, the budget/deficit, safety/security, and immigration. Iowa respondents named the economy, safety/security, the budget/deficit, terrorism/ISIS, and immigration.

Eighty-seven percent in both states said the current negotiations with Iran were unlikely to prevent the Islamic Republic from pursuing a nuclear weapon. Three-quarters of respondents in Iowa and 87 percent in South Carolina said they would support military action in order to prevent Iran from obtaining nuclear weapons.

Paul, who announced his presidential bid on Tuesday, has been forced to address questions about his foreign policy positions in response to critical ads from the Foundation for a Secure and Prosperous America.

One of the ads replays a 2007 interview with Paul during which he said it was "ridiculous to think" Iran is a threat to the United States or Israel.

Paul pushed back on the criticism in an interview with Fox News host Sean Hannity on Tuesday.

"I would say that almost every element of the ad is a lie," Paul said. "I have no idea really who these people are, but I would say they're part of the neocon community."

When NBC’s Savannah Guthrie pressed the presidential hopeful on his prior comments, Paul said his views on Iran’s threat level have since changed.

"2007 was a long time ago," said Paul. "We’re talking about a time when I wasn’t running for office, when I was helping [my father Ron Paul] run for office."

Lisa Boothe, a spokesperson for the Foundation for a Secure and Prosperous America, said Paul’s response does not stand up to scrutiny.

"What these ads do is they capture previous statements that he has made himself," she said. "It’s hard to refute those statements when they’re in your own words."

"It’s Senator Rand Paul who has opposed new sanctions," Boothe added. It’s Senator Rand Paul who has said he supports Obama’s negotiations with Iran. It’s Senator Rand Paul who has previously stated Iran does not pose a national security threat to the United States or our ally Israel."

Paul has not taken a definitive position on the Obama administration’s framework nuclear agreement with Iran. A spokesman for Paul told Bloomberg on Tuesday that he was waiting for more details to come out.

The senator said he would "oppose any deal that does not end Iran’s nuclear ambitions and have strong verification measures," in a speech announcing his presidential run on Tuesday.

One of Paul’s main foreign policy advisers, former Ambassador Richard Burt, endorsed the Obama administration’s nuclear framework with Iran last Friday.

Burt called the reported details of the agreement "a historic achievement" and "a huge step forward" in a statement on behalf of Global Zero, an anti-proliferation group.

"Its terms are better than most observers anticipated: no uranium enrichment for 15 years, bigger cuts in centrifuges, rigorous verification provisions, with several in place for 15 years or longer," said Burt, who is the U.S. chair of Global Zero.

He said the agreement was being opposed by "hardliners in both countries."

A spokesperson for Paul did not respond to a request for comment.