Florida Republican Sen. Marco Rubio is calling for the Justice Department to investigate former Secretary of State John Kerry for meeting with high-level Iranian officials after leaving his position when President Donald Trump took office.

Kerry, the architect of the Iran Nuclear Deal that most Republicans oppose, was President Obama's top diplomat during the latter half of his administration. The Boston Globe reported in May that Kerry met with Iranian Foreign Minister Javad Zarif more than a year after leaving office to discuss ways to keep the deal intact.

In recent days, current Secretary of State and Rubio ally Mike Pompeo blasted the meetings as "beyond inappropriate" and Trump took to Twitter to voice his displeasure.

"John Kerry had illegal meetings with the very hostile Iranian Regime, which can only serve to undercut our great work to the detriment of the American people," Trump tweeted. "He told them to wait out the Trump Administration! Was he registered under the Foreign Agents Registration Act? BAD!"

Rubio's letter, which was first reported by Fox News, asks Attorney General Jeff Sessions to investigate whether Kerry violated the Logan Act, a law that prohibits unauthorized individuals from negotiating with foreign governments.

"Last week former Secretary Kerry publicly admitted that he has met with Iranian foreign minister Javad Zarif 'probably three or four times' including in the United States, since leaving office," Rubio's letter said. "The Department of Justice should therefore make a determination on whether or not former Secretary of State John F. Kerry's recent actions related to the [Iran Deal] potentially violate the Logan Act or the Foreign Agents Registration Act."

Kerry, a former U.S. Senator, unsuccessfully ran for president in 2004 before serving as secretary of state.