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Members of the House foreign affairs committee's sub-panel on the Middle East, North Africa and Central Asia met parents of three Israeli-American men who were serving in the Israeli army and were taken hostage on October 7.
Ronen and Orna Neutra are the parents of Omer, 22, from Plainview, New York, who volunteered to serve in the army. He was a tank commander near the border with Gaza.
"It's unimaginable that we find comfort in the fact that he was taken hostage and not murdered on that day," Ms Neutra said.
She said the Red Cross had not been able to visit to Omer since he was taken hostage.
US officials say nine US citizens are believed to be held in Gaza.
"We have to get our American citizens home to safety," committee chairman Mike McCaul said.
"I will not rest and members on this committee will not rest until we bring every American back home to the United States."
The meeting comes on the sixth day of a truce between Israel and Hamas, which has put a temporary pause to more than seven weeks of fighting.
The truce, which was brokered by Qatar, Egypt and the US, brought to a halt Israeli bombardment on Gaza that began after Hamas gunmen attacked Israel, killing 1,200 people and kidnapping about 240.
Israel's military campaign in Gaza, by air, sea and ground, has killed 15,000, most of them civilians, and reduced much of the coastal enclave to rubble.
About 60 Israeli hostages have been released so far, in exchange for 180 Palestinian detainees.
In late October, Hamas released two US citizens, Judith Tai Raanan, 59, and her daughter Natalie, 17.
Avigail Idan, 4, a dual Israeli-American citizen, was released at the weekend. Her parents were killed on October 7.
Yael Alexander, whose son Edan, also a soldier, is among the hostages, said: "I am hoping that he will come home to us."
Hamas has also released more than 20 others it held captive, mostly Thais, in an agreement outside the scope of the truce deal, according to officials.
US Secretary of State Antony Blinken is due to arrive in Israel this week, in his third visit since the war began, to try to prolong the truce.
Ruby and Hagit Chen's son Itay was also serving in the Israeli army as a volunteer.
"Time is ticking and is not in our favour," Mr Chen said. "We want to be whole again with our families."