Under pressure, Biden works for ceasefire in Israel-Gaza violence 

President Joe Biden and aides worked behind the scenes on Monday pressing for a ceasefire between Israel and Hamas amid what one source said was frustration over Israel's bombing of a Gaza building that housed some news organisations. 

Biden is facing growing pressure from lawmakers in his own Democratic Party to play a more vocal role, but US officials say he and his team have opted for a quieter effort, talking with Israeli officials and US allies in the Arab world. 

Watch: US asks Israel for 'justification' for strike on media building

"Our calculation at this point is that having those conversations behind the scenes ... is the most constructive approach we can take,” White House spokeswoman Jen Psaki told reporters. 

Biden spoke by phone with Israeli Prime Minister Benjamin Netanyahu, their third conversation since the violence erupted. 

The White House said Biden 'encouraged Israel to make every effort to ensure the protection of innocent civilians' and that the two leaders 'discussed progress in Israel’s military operations against Hamas and other terrorist groups in Gaza’. 

"The president expressed his support for a ceasefire and discussed US engagement with Egypt and other partners towards that end," a White House statement said. 

Supporters of the Biden administration demanded quicker action. 

“We’re really frustrated that the administration is not moving with more urgency,” said Logan Bayroff, spokesman for J Street, a liberal pro-Israel lobbying group. 

Twenty-eight senators, more than half of the Democratic caucus, issued a statement on Sunday calling for an immediate ceasefire 'to prevent any further loss of civilian life and to prevent further escalation of conflict.' 

Senate Majority Leader Chuck Schumer said on Monday, he also wanted to see a ceasefire reached quickly. 

The Biden administration has increasingly relied on Egypt because of its influence with Hamas, whose rocket barrages into Israeli cities have prompted a fierce response from Israel and led to the biggest outbreak in hostilities since 2014.  

The administration would like to get on a glide path to de-escalation in coming days, leading to what a source familiar with the situation called a humanitarian pause in the violence to let relief assistance be delivered to Gaza and build a sustainable calm. 

The United States was believed to be preparing significant initiatives on Gaza humanitarian reconstruction, the source said. 

(With inputs from agencies)