DUBAI, United Arab Emirates (AP) — Some $6 billion of Iranian assets once frozen in South Korea is in Qatar, a key element for a planned prisoner swap between Tehran and the United States, an Iranian official said Monday.

Nasser Kanaani made the comment during a news conference aired on state television, but the feed cut immediately after his remarks without explanation.

Iranian news agencies immediately afterward reported, quoting Kanaani, that the prisoner swap would be done on Monday. There was no other information immediately released by the agencies.

The announcement by Kanaani comes weeks after Iran said that five Iranian-Americans are now under house arrest as part of a confidence-building move while Seoul allowed the frozen assets, held in South Korean won, to be converted into euros. That money was then sent to Qatar, an interlocutor between Tehran and Washington in the negotiations.

The swap unfolded amid a major American military buildup in the Persian Gulf, with the possibility of U.S. troops boarding and guarding commercial ships in the Strait of Hormuz, through which 20% of all oil shipments pass.

The deal has also already opened President Joe Biden to fresh criticism from Republicans and others who say that the administration is helping boost the Iranian economy at a time when Iran poses a growing threat to U.S. troops and Mideast allies. That could carry over into his reelection campaign as well.