United Nations secretary general Ban Ki-moon has renewed his appeal to Israel and Hamas to halt the fighting in Gaza immediately and show respect for civilians and the rapidly deteriorating humanitarian situation.
Religious leaders, including visiting bishops from the USA, have also kept up pressure for a cessation of hostilities.
The calls came as Israeli ground forces and tanks moved deeper into built up urban areas and launched air strikes across the Gaza Strip for a 17th day in succession.
Nearly 30 mostly home-made rockets or mortars were fired on Israel from Gaza on Monday 12 January, but no fatalities resulted.
Prime Minister Ehud Olmert said Palestinian militants will keep on feeling Israel's "iron fist" as long as Hamas fires the rockets at Israel.
Meanwhile, Bishops of the Evangelical Lutheran Church in America (ELCA) and the Evangelical Lutheran Church in Canada (ELCIC) have met with Israeli government and religious officials as part of a pilgrimage to the Middle East.
They made it plain that while they opposed attacks on Israel, they also condemned the disproportionate use of force by Israel in Gaza and joined international calls for a ceasefire.
But a senior Hamas leader, Ismail Haniya, said the group was "approaching victory", according to the BBC.
"After 17 days of this foolish war, Gaza has not been broken and Gaza will not collapse," he said in a televised address from a secret location in Gaza.
Both Hamas and Israel rejected last week's UN Security Council resolution calling for an immediate ceasefire.
Palestinian medical sources say 910 people have been killed in Gaza so far, of whom 292 were children and 75 were women. Israeli officials say 13 Israelis, including three civilians, have been killed.
Hanna Massad of the Gaza Baptist Church has told reporters and overseas supporters that life is very difficult for the 2,500 Christians in Gaza. His own church has been caught in the crossfire.
Massad said at the end of last year that most American Christians know that the state of Israel was established in 1948, but fewer are aware that when that happened 700,000 Palestinians, including 55,000 Christians, were made refugees.