DUBAI, United Arab Emirates (AP) Iran has transferred five Iranian-Americans from prison to house arrest, U.S. officials said Thursday. The move comes after Tehran has spent months suggesting a prisoner swap with Washington in exchange for billions of dollars frozen in South Korea.

Iranian officials at the United Nations confirmed the deal to The Associated Press, saying that the prisoner release marks a significant initial step in the implementation of this agreement.

Iran also acknowledged that the deal involved $6 billion to $7 billion frozen in South Korea. The U.N. mission said that money would be transferred to Qatar before being sent onto Iran if the agreement goes through.

The complicated, multinational deal comes amid months of heightened tensions between Iran and the U.S. A major American military buildup in the Persian Gulf is underway, with the possibility of armed U.S. troops boarding and guarding commercial ships traveling through the crucial Strait of Hormuz , through which 20% of all oil traded passes.

It remains unclear whether the transfer of the Iranian-Americans guarantees that they will make it home. Iran in past months has overstated progress in talks, likely conducted with mediation from Oman and Qatar, on a potential trade.

The U.S. in March called remarks by Iranian Foreign Minister Hossein Amirabdollahian that a deal for a swap was close a cruel lie.

U.S.-based lawyer Jared Genser identified three of the transferred prisoners as Siamak Namazi, Emad Sharghi and Morad Tahbaz. Genser, who has represented Namazi, did not identify the fourth and fifth prisoners. The five likely will be held at a hotel under guard until they possibly leave Iran, Genser added.

The move by Iran of the American hostages from Evin Prison to an expected house arrest is an important development, Genser said in a statement. While I hope this will be the first step to their ultimate release, this is at best the beginning of the end and nothing more. But there are simply no guarantees about what happens from here.

Sharghis sister, Neda Sharghi, also acknowledged the transfer.

My family has faith in the work that President Biden and government officials have undertaken to bring our families home and hope to receive that news soon, she said in a statement. Until that point, I hope you can understand that we do not think it will be helpful to comment further.

Adrienne Watson, a spokesperson for the White Houses National Security Council, acknowledged the prisoners move to house arrest and described the negotiations for their release as ongoing and delicate.