US President Joe Biden reiterated his backing for Israel and apparently accused a "terrorist group" of causing a recent deadly explosion at a hospital in Gaza as he visited Tel Aviv on Wednesday to stress America's solidarity with Israel following the Hamas militant group's attack this month.

Biden arrived in Tel Aviv Wednesday morning amid a spike in tensions over Tuesday's blast at the Al-Ahli Arab Hospital in the Hamas-controlled enclave, which left hundreds of innocent civilians dead.

Hamas claimed that the blast was caused by an Israeli air strike. Israel has denied responsibility, arguing a botched Islamic Jihad rocket launch led to the tragedy.

"I was outraged and saddened by the enormous loss of life yesterday in the hospital in Gaza," Biden told a press conference following his talks with Israeli Prime Minister Benjamin Netanyahu and Israel's war cabinet.

"Based on the information we've seen to date, it appears as a result of an errant rocket fired by a terrorist group in Gaza," he added.

He stressed that the United States "unequivocally" stands for the protection of civilian life during conflict, while noting that he asked the Israeli cabinet to agree to the delivery of "life-saving" humanitarian aid to civilians in Gaza.

He also announced $100 million of new US funding for humanitarian assistance to both Gaza and the West Bank.

"I truly grieve for the families who were killed or wounded by this tragedy. People of Gaza need food, water, medicine and shelter," he said.

Biden redoubled his backing for Israelis, saying he plans to ask Congress for an "unprecedented" support package for the country's defense.

During his talks with Netanyahu and other Israeli officials, his message of support for Israel reverberated.

"I want you to know you're not alone ... we will continue to have Israel's back as you work to defend your people," Biden told Israel's war cabinet.

Biden also mentioned the declaration that Israeli founders made over 75 years ago that their country would be one that is based on "freedom, justice and peace."

"The United States stands with you in defense of that freedom, to pursue that justice and support that peace today, tomorrow and always. We promise you," he said.

Biden's high-stakes trip focused on reaffirming America's solidarity with Israel, preventing the ongoing conflict from escalating and exploring ways to minimize civilian damage.

His trip coincided with the US Treasury Department's announcement on fresh sanctions against ten key Hamas group members, operatives and financial facilitators in Gaza and elsewhere, including Sudan, Turkey, Algeria and Qatar.

The rise in tensions over the hospital explosion was a setback to the Biden administration that has sought to reduce regional tensions while moving to ensure the flow of humanitarian aid to the blockaded Gaza enclave.

Biden had planned to visit Jordan for talks with Arab leaders, but the visit was called off following the blast at the hospital.

Meanwhile, Secretary of State Antony Blinken held phone talks with Palestinian Authority President Mahmoud Abbas to express "profound condolences for the civilian lives lost in the explosion at the hospital in Gaza, according to Matthew Miller, a spokesperson of the State Department.

"The Secretary emphasized that the United States unequivocally condemns all terrorism and stressed the United States' firm commitment to upholding the law of war, to include important protections for civilians," Miller said in a statement.

"The Secretary and the President discussed continuing US efforts to coordinate the provision of urgent, life-saving humanitarian assistance to civilians in Gaza, in tandem with partners, and efforts to prevent the conflict from spreading," he added. (Yonhap)