The US president spoke with Israeli PM Benjamin Netanyahu as violence continues.
, Mr Biden "encouraged Israel to make every effort to ensure the protection of innocent civilians".
In the UK, Prime Minister Boris Johnson's spokesman said Israel must avoid civilian casualities, but expressed concern that "Hamas is again using civilian infrastructure and populations as cover for its operations". The outbreak of violence began after weeks of rising Israeli-Palestinian tension in occupied East Jerusalem that culminated in clashes at a holy site revered by both Muslims and Jews. Hamas, which controls Gaza, began firing rockets after warning Israel to withdraw from the site, triggering retaliatory air strikes.Israel continued to pummel Gaza with air strikes on Monday and Palestinian militants launched rockets at Israeli cities.
"The situation in Gaza is becoming worse and worse, the system is being collapsed and stretched because also we are complaining and suffering from the fuel," he added.An Israeli tech executive and father of three, Eitan Singer, told the BBC Hamas - Mr Abbas' Islamist rivals who control Gaza and were running in the elections - react angrily to the postponement.Rockets are fired from Gaza at Israel, which responds with air strikes after a relative period of calm between Israel and the Palestinian enclave.20 April