"We continue to demand that Syrian officials fulfill their obligations under the Vienna Convention on Consular Relations to acknowledge the detention of Austin and every other U.S. national held in Syria, a responsibility under international law and an important step in securing their release," Blinken said. Another American, Majd Kamalmaz, was detained at a checkpoint in Damascus in February 2017 and has not been heard from since.

Biden met with Austin Tice's parents, Marc and Debra, in early May. Following that meeting, Marc Tice told CNN's Jake Tapper in an interview on the "The Lead" that Biden told them "he supported the efforts that are underway and other efforts that may create positive movement" to get Austin home.

"One of the efforts underway is pushing to get engagement and engagement that sustained," between the US and Syria, Marc Tice said at the time. The two nations do not have diplomatic relations.

In his statement Wednesday, Blinken said that "Special Presidential Envoy for Hostage Affairs Roger Carstens will continue to engage with the Syrian government in close coordination with the White House, Hostage Recovery Fusion Cell, and our team here at the State Department."

Carstens secretly traveled to Damascus and met with Assad regime officials in 2020 under the Trump administration. In May of this year, he met with Abbas Ibrahim, a top Lebanese security official, in Washington "to discuss US citizens who are missing or detained in Syria," State Department spokesperson Ned Price said at the time. Ibrahim, the chief of Lebanon's General Security Directorate, has played a role in securing the release of American detainees in the past, including Sam Goodwin from Syria and Nizar Zikka from Iran.