'Amnesty International USA is particularly dismayed at the lopsided response by the US government to the recent violence and its lackadaisical efforts to ameliorate the humanitarian crisis in Gaza,' the rights group said in a letter to Secretary of State Condoleezza Rice.
The strongly worded criticism said Amnesty is 'deeply concerned' that US-supplied weapons are being used in the heavy bombing campaign against militant Hamas sites in the densely populated Palestinian territory.
'The United States must suspend the transfer of weapons to Israel immediately and conduct an investigation into whether US weapons were used to commit human rights abuses,' Amnesty said.
Washington is widely seen as having given a diplomatic green light to the Israeli offensive, which follows attacks by Hamas, the ruling power in Gaza.
Dr Rice on Friday said Washington was pressing for a ceasefire in which the key element would be stopping Hamas firing rockets into Israel.
Since Israel unleashed its air and sea campaign six days ago, at least 430 Palestinians have been killed, including 65 children, and 2,250 others wounded, according to Gaza medics.
Four people have been killed in Israel in a barrage of highly inaccurate rockets fired by Hamas.
Israel is a close ally and aid recipient of the United States, as well as a major weapons client. -- AFP