Iran and the United States will hold the second round of negotiations on April 19 after the two sides concluded their "indirect" talks on Saturday in the Omani capital of Muscat in a "constructive" atmosphere, according to the Iranian Foreign Ministry.

The two-and-a-half-hour talks between Iranian Foreign Minister Seyed Abbas Araghchi and U.S. Special Envoy to the Middle East Steve Witkoff centered on Tehran's nuclear issue and sanctions relief, said the ministry in a statement.

It added that the two sides agreed to continue the talks next week, noting that when leaving the negotiations venue, the heads of the two countries' delegations spoke for a few minutes in the presence of the Omani foreign minister.

In an address to reporters in Muscat following the talks, Araghchi said the first round of the talks was "constructive and held in a calm and very respectful atmosphere."

"No inappropriate language was used and the two sides demonstrated their commitment to advancing the talks until the achievement of a mutually favorable agreement from an equal position," he added.

The minister revealed that the second round of the talks "are scheduled to be held at the same level next Saturday, but the venue will probably not be here (Muscat)."

The two sides had decided to enter a general framework needed for an agreement in the next round, Araghchi said, noting that both sides favored an agreement that would be reached as soon as possible.

He added that in the next round of the talks, "we will try to enter the negotiations' agenda, which will of course have a timetable alongside it," expressing hope that in the upcoming negotiations, the two sides would be able to finalize a basis for starting "real talks."

The talks in Muscat came after U.S. President Donald Trump stated in early March that he had sent a letter to Iranian leaders -- via the United Arab Emirates -- proposing negotiations on Iran's nuclear program.

Iran later confirmed receiving the letter and left the door open for indirect engagement.