Former Secretary of State John Kerry’s secret negotiations to try to preserve the Iran nuclear deal went well beyond what most past secretaries of state have done, a veteran expert on the Middle East says.

“Many former secretaries of state remain actively engaged in foreign affairs,” Jim Phillips, a senior research fellow at The Heritage Foundation, told The Daily Signal. “To my knowledge, one has never undermined a succeeding administration to this degree, especially with such a long-term adversary as Iran.”

President Donald Trump announced in May that the United States was withdrawing from the Iran deal, which also included Britain, France, Germany, China, and Russia. Kerry oversaw the Obama administration’s negotiations of an agreement to slow Iran’s efforts to build nuclear weapons.

Kerry, a former U.S. senator from Massachusetts who was the Democrats’ presidential nominee in 2004, said Wednesday on commentator Hugh Hewitt’s radio show that he met with Iranian Foreign Minister Javad Zarif “three or four times” about salvaging the agreement.

“I told him, ‘Look, you guys need to recognize that the world does not appreciate what’s happening with missiles, what’s happening with Hezbollah, what’s happening with Yemen. You’re supporting, you know, an ongoing struggle there,’” Kerry said.

“They say they’re prepared to negotiate and to resolve these issues,” he told Hewitt. “But the [Trump] administration has taken a very different tack.”

Kerry later told Fox News Channel’s Dana Perino that he met with Zarif two or three times.

Kerry may have assisted Iran with one goal, Phillips said.

“Iran wanted to drive a wedge between the United States and European allies,” Phillips, who specializes in Middle Eastern affairs, said. “This undermines the Trump administration without producing any benefits for the United States.”

Some critics allege that Kerry, who has no official U.S. government authority, violated the Logan Act of 1779, which states:

Any citizen of the United States, wherever he may be, who, without authority of the United States, directly or indirectly commences or carries on any correspondence or intercourse with any foreign government or any officer or agent thereof, in relation to any disputes or controversies with the United States, or to defeat the measures of the United States, shall be fined under this title or imprisoned not more than three years, or both.

Phillips noted that no one has been prosecuted under the Logan Act, so it would be a difficult case to make.

“We’re not going to comment,” said a White House National Security Council spokesman. “That a former secretary of state tried to interfere with current policy says everything.”

Some political observers say Kerry is considering challenging Trump in the 2020 presidential election.

In his interview Wednesday with Hewitt, Kerry confirmed previous reports that he met with Iranian officials. Those reports prompted Trump in May to charge Kerry of conducting “shadow diplomacy.”

Kerry served as secretary of state during Barack Obama’s second term as president, from 2013 through 2016.

In 2015, he headed negotiations of the Joint Comprehensive Plan of Action, the U.S.-led multilateral agreement with Iran. The deal removed sanctions on Iran in return for the Islamist regime’s ceasing to develop nuclear weapons for 10 years.

“People talk about the Iran deal as Obama’s legacy, but it has Kerry’s fingerprints all over it,” Heritage’s Phillips said. “He also is responsible for the Syrian chemical weapons agreement. Syria violated that from the start. He didn’t seem aware the Iran deal could turn out the same.”