The US says it has intelligence that Hamas has a command centre under Al-Shifa hospital in Gaza City.
National Security spokesman, John Kirby, said the group stored arms there and were prepared for an Israeli attack.
This is the first time the US has independently backed claims by close ally, Israel, that Hamas uses hospitals to hide its bases. Hamas denies this.
The statement came as Israel faced mounting global pressure to protect civilians trapped in the hospitals.
US President, Joe Biden, said that Al-Shifa hospital “must be protected” from intense fighting around the complex, and UK Prime Minister, Rishi Sunak, said Israel must act within international law.
The area around Al-Shifa, Gaza’s biggest hospital, has become the focus of fighting in recent days. Thousands of people are believed to be sheltering there.
Mr Kirby said the US had its own intelligence, which had come from a variety of sources, suggesting that Hamas and Islamic Jihad used hospitals in the Gaza Strip and tunnels underneath them to conceal military operations and hold hostages.
Previously, the US administration had only cited open-source intelligence and would not confirm that it had its own sources for this.
“Hamas and Palestinian Islamic Jihad members operate a command and control node from Al-Shifa in Gaza City,” he said.
“They have stored weapons there and they are prepared to respond to an Israeli military operation against that facility.”
Mr Kirby said this showed how challenging the Israeli operation was as “Hamas has deeply embedded itself within the civilian population”.
“To be clear, we do not support striking a hospital from the air and we do not want to see a firefight in the hospital where innocent people, helpless people, sick people are simply trying to get the medical care that they deserve, not to be caught in a crossfire. Hospitals and patients must be protected,” he said. —BBC