(NewsNation) — The father of unreturned Israeli American hostage Itay Chen is disappointed not to receive a call confirming the fate of his son.

On Monday, Hamas released 20 living and four deceased hostages, but Israelis are still waiting for the release of 24 more deceased hostages.

“We understood that the agreement had some loopholes when it came to the deceased hostages, that it was based on ‘best effort,’ and it’s very difficult to quantify what ‘best effort’ is,” Ruby Chen, whose son is believed to be dead, told “Elizabeth Vargas Reports.”

With 72 hours having passed since the release of the living hostages, Chen believes more should have been done. He met with President Trump on Monday, reiterating his desire for his son and other hostages to be returned to their families.

“The call now is that the job is not done. I expect this administration, that has done a wonderful job when it comes to bringing U.S. citizens from captivity, I expect them to do the same thing with my son also.”

Chen urged the United States to “place an emphasis on its citizens” to ensure the remaining hostages are returned.

Israel plans to halve aid to Gaza because of Hamas’s slower-than-expected release of deceased hostages, per The Associated Press.