The International Committee of the Red Cross, which has faced criticism for not doing enough to release the hostages in Gaza, stresses it has no "superpowers" and relies on the warring parties for access.
"From time to time, we have to tell people we're not bulletproof," ICRC spokesman Jason Straziuso told AFP.
"We don't have superpowers. We can only take humanitarian action when the authorities in a given area give us the permission."
In recent days, amid the temporary truce in Gaza, the Geneva-based organization's vehicles have brought dozens of hostages held by Hamas out of the Palestinian enclave.
On October 7, Hamas launched an attack on Israel, killing 1,200, according to Israeli authorities.
In response, Israel unleashed a severe air and ground military campaign that the Hamas government says has killed nearly 15,000 in Gaza, mostly civilians including more than 6,000 children.
The ICRC, founded 160 years ago, has been criticized for not taking part in negotiations that led to their liberation, and for not visiting those remaining in captivity in Gaza. It has also faced criticism for not pressuring Israel to liberate more Palestinian prisoners, and for not bringing more aid into Gaza.
Straziuso said much of the criticism showed "a lack of understanding of how we work or the limitations of our work".
"We are not an intelligence agency," he said stressing that “We couldn't possibly just simply start walking through Gaza and trying to locate hostages.”
Such an action, he said, "could directly put the hostages in danger and it could put our team in danger".
Julie Billaud, an associate professor at Geneva's Graduate Institute of International and Development Studies, said "The humanitarian organizations in general and ICRC in particular cannot substitute the political work needed" to end this war.
Marco Sassoli, an international law professor at Geneva University, meanwhile explained that if international humanitarian law was being respected, "hostages, unlike prisoners, must be freed unconditionally and without negotiation", he told AFP.
Thus, "the ICRC can offer its services as a neutral intermediary, but it will not negotiate the hostages' liberation".
Ever since Russia's full-scale invasion of Ukraine in February 2022, Ukrainian President Volodymyr Zelensky has repeatedly and publicly questioned the Committee's lack of access to prisoners of war held by Moscow.
Sassoli lamented that there today was "less and less understanding of neutrality", with everyone, including the ICRC, pressured to "take a position and say there are bad guys and good guys".
"If the ICRC only negotiates with good guys, they will have barely anyone to negotiate with in armed conflicts," the professor warned.