A prisoner swap between the United States and Iran was expected to take place on Monday, according to a spokesman for the Iranian Foreign Ministry, after two years of high-stakes negotiations.

As part of the deal, the United States had agreed to unfreeze $6 billion in Iranian oil revenue and dismiss federal charges against several Iranians accused of violating U.S. sanctions.

The announcement at a news conference in Tehran from the spokesman, Nasser Kanaani, came as President Biden and Ebrahim Raisi, Iran’s president, were to attend the annual United Nations General Assembly meeting of world leaders on Tuesday. The spokesman’s remarks were published on the website of the Iranian news agency ISNA.

Mr. Kanaani said five Iranians, several of whom are permanent residents of the United States, were expected to be released. It was not immediately clear exactly how many of the Iranians would return to Iran, although Mr. Kanaani said it would be two.