Tel Aviv, Dec 8 : US President Joe Biden has expressed deep concerns about the 135 Israeli hostages who are in the custody of Hamas. Israel Prime Minister's office in a statement said that Biden had a long telephonic call with Benjamin Netanyahu in which he shared his concerns about the fate of the Israeli hostages. Biden has, according to Israel PMO, reiterated the position of the US that the Red Cross be allowed to visit the hostages and take stock of their physical and mental health. The White House in a statement said, "He noted that it was Hamas's refusal to release young women civilian hostages that led to a breakdown in the humanitarian pause. The leaders agreed to remain deeply engaged to pursue every possible opportunity to free the remaining hostages. "The President underscored the importance of the continuous and sustained flow of humanitarian aid into Gaza. He welcomed the recent Israeli decision to ensure that fuel levels will meet requisite needs, but stressed that much more assistance was urgently required across the board. The President emphasized the critical need to protect civilians and to separate the civilian population from Hamas including through corridors that allow people to move safely from defined areas of hostilities. "President Biden reiterated his concern about extremist violence committed against Palestinians and the need to increase stability in the West Bank. "The President and the Prime Minister agreed to remain in regular consultation both directly and through their respective national security teams. It may be noted that the Israel Defense Forces (IDF) has been involved in a ground invasion in Gaza since October 27 after Hamas terrorists attacked Southern Israel and slaughtered 1,200 people, including children, women and elderly and took hundreds as hostages. /IANS