An Iranian detained in Italy who is wanted on terrorism charges by Washington was denied release on Thursday, signaling no quick end to the ordeal of an Italian journalist held by Iran for a likely prisoner swap.

Mohammad Abedini Najafabadi was arrested on December 16 at Malpensa Airport by Italian authorities after arriving from Istanbul and is currently held at Opera prison.

The attorney general of Milan, Francesca Nanni, rejected his conditional release citing a high flight risk.

The arrest of Italian journalist Cecilia Sala in Tehran is widely regarded as Iran's retaliation for Najafabadi’s detention.

Iran has officially confirmed Sala’s arrest. The 29-year-old works for Il Foglio and the podcast company Chora Media. She has been detained for "violating the laws of the Islamic Republic," with no further specifics given.

Iran's ambassador to Italy, Mohammad Reza Sabouri, on Thursday met with Italian Foreign Ministry secretary-general Riccardo Guariglia to discuss the cases of Abedini and Sala, according to Iran's official state media, IRNA.

US authorities allege that Najafabadi supplied materials for a deadly Iran-linked drone attack on American troops in Jordan.

Iran's consulate in Italy had requested Italian authorities to allow Abedini to leave detention facilities in return for guarantees that he'd stay in a known location.

Milan's attorney general on Thursday argued that Iranians' guarantees---including housing and financial assistance, potential travel restrictions and mandatory check-ins---would be insufficient to address the risk of flight for the individual sought by the United States for extradition.

She noted that the charges leveled by US authorities would undergo a comprehensive review once the necessary documentation is provided.