The United States called on Egypt to use its sway with the Palestinians to try to end the violence from Gaza, adding that Hamas must stop its rocket attacks on Israel.
"We ask Egypt to use its influence in the region to help de-escalate the situation," deputy State Department spokesman Mark Toner told journalists.
But he insisted "the onus was on Hamas" to stop rocket attacks into southern Israel after the Jewish state on Wednesday (local time) launched Operation Pillar of defence, its biggest military campaign against Gaza in nearly four years.
Seven Palestinians and three Israelis were killed Thursday (local time) in a wave of unrelenting cross-border fighting as Israel pressed its vast air offensive.
US Secretary of State Hillary Clinton had spoken with her Egyptian counterpart Mohammed Amr on Wednesday, Toner said.
"Both we and the Egyptians agree there needs to be a de-escalation, and we urged the government of Egypt to take steps to support that kind of de-escalation," he said
"We need to see the violence just stop. We need to see Hamas stop its rocket attacks on Israel so we can end the violence."
Obama spoke with Egyptian President Mohamed Morsi on Wednesday in recognition of Egypt's "central role in preserving regional security," the White House said.
Morsi, an Islamist elected in June after ex-president Hosni Mubarak's overthrow in 2011, has promised to take a harder line than his predecessor, who was accused of doing little to stop Israel's Gaza assault beginning in 2008.
Egypt in 1979 became the first Arab country to sign a peace treaty with Israel.
The president's Muslim Brotherhood movement, which is closely aligned with the Hamas rulers of neighboring Gaza, has called for an economic boycott of Israel.