“Hamas is going to make the decision about whether they’re prepared to release another 10 hostages. Israel has put its cards on the table. They’re prepared to extend the pause in the fighting,” Sullivan said.

“So the ball is in Hamas’ court. Will Hamas step up and release another 10 hostages? If they won’t, then they’re the ones choosing to bring an end to the pause in fighting, not Israel,” he added, noting that President Joe Biden is set to speak with Israeli Prime Minister Benjamin Netanyahu on Sunday.

The agreement between Israel and Hamas has so far allowed some desperately needed to reach besieged northern Gaza, and as of Sunday morning had resulted in the release of 41 hostages from captivity in the Gaza Strip, and 78 Palestinian prisoners from Israel.

Hamas is still believed to holding approximately 200 hostages who were taken during the Oct. 7 attack. Israel has more than 8,000 Palestinians imprisoned across the state — about 5,000 of whom were arrested before Hamas’ attack this fall.

Americans are among those still held hostage by Hamas, though Sullivan said Sunday the U.S. “has reason to believe” that at least one American will be among those released Sunday.

Though Sullivan did not disclose the identity of the American expected to be released, Qatari Prime Minister Sheikh Mohammed Bin Abdulrahman al-Thani told CBS’ Margaret Brennan it was 4-year old Abigail Mor Edan. Her parents were both killed in her presence during the Oct. 7 attack

“The initial hostage deal involves the release of women and children, and there are three Americans in that category — two women and one young child — and we have reason to believe that one of those Americans will be released today,” Sullivan said. “But until we see her out safely from Gaza, in the hands of the authorities and ultimately in the hands of her family, then we won’t be certain. But we have reason to believe that there will be one released today.”