Iran's Foreign Minister Seyed Abbas Araghchi on Saturday said the negotiations with U.S. delegations in Rome were held in a "constructive" atmosphere and are making progress, according to Iran's IRIB news agency.

He made the remarks at the end of the second round of the Omani-mediated indirect talks between Iranian and U.S. delegations, headed by him and U.S. Special Envoy to the Middle East Steve Witkoff respectively, on Iran's nuclear program and removal of Washington's sanctions.

Araghchi described the four-hour meeting as "good" and "forward-moving," adding that both sides had reached a better understanding of several key principles and objectives.

He also noted that technical negotiations at the expert level are set to begin in Oman by Wednesday, where the details of the agreement's framework may be discussed.

He added that the negotiators would meet in Oman next Saturday again to discuss the result of the experts' work.

The just concluded indirect talks were the second round between U.S. and Iranian delegations. The first round of the talks was held last Saturday in the Omani capital Muscat, which were described by both sides as "constructive."

The talks followed U.S. President Donald Trump's threats to bomb Iran if the Middle Eastern country does not accept his offer for talks outlined in a letter sent to Iran's leadership in early March.

Iran signed a nuclear deal, formally known as the Joint Comprehensive Plan of Action, with six major countries -- Britain, China, France, Germany, Russia, and the United States -- in July 2015, accepting restrictions on its nuclear program in return for sanctions relief.

However, the United States withdrew from the deal in May 2018 and reinstated sanctions, prompting Iran to scale back some of its nuclear commitments. Efforts to revive the nuclear deal have not achieved substantial progress.