Washington - US President George W Bush spoke with Palestinian President Mahmoud Abbas on Tuesday over efforts to achieve "a sustainable ceasefire" to end the fighting in the Gaza Strip, the White House said.

Bush also spoke with Palestinian Prime Minister Salam Fayyad and Egyptian President Hosny Mubarak, said Gordon Johndroe, a White House spokesman.

"They agreed that for any ceasefire to be effective, it must be respected, particularly by Hamas," Johndroe said in Crawford, Texas, where Bush is vacationing.

Johndroe reiterated demands on Hamas to stop launching rockets against Israel, blaming the Islamic militants for the conflict and massive military response by the Israelis.

"These sides know how to end this: Hamas stops firing rockets and Israel will not see a need to protect its people from rocket attacks," Johndroe said.

Washington will only back a ceasefire that is lasting and adhered to by Hamas, he said.

"We don't want a ceasefire agreement that isn't worth the paper it's written on," he said.

Israel was in its fourth day of airstrikes in the Gaza Strip, which is controlled by Hamas. Fighting erupted after Hamas declared earlier this month that it would not extend a six-month ceasefire.

At least 369 people have died so far in Gaza. The United States has urged Israel to avoid civilian casualties in the conflict and called on both sides to ensure humanitarian aid reaches the tiny enclave.

Meanwhile, the US State Department said it was releasing 85 million dollars in funding to assist Palestinian refugees in the Middle East. The money will be distributed to the UN Relief and Works Agency for Palestine Refugees. (dpa)