"We're fed up," said Said Kamal, the deputy secretary-general for Palestinian affairs at the Cairo-based pan-Arab organisation.
"We can't keep count any more of the number of times the Americans have used their veto on behalf of Israel at the security council," he said on Thursday.
The US on Tuesday vetoed the draft, which called for the "immediate cessation of all military operations in the area of northern Gaza and the withdrawal of the Israeli occupying forces from that area".
It did not, however, refer to rocket attacks on Israeli soil from Gaza by Palestinian fighters, which the Israeli government says the military operation is intended to quell.
Al-Rai: US veto is a 'green light
to pursue massacre' in Gaza
Any attempt by the international community to back the Arab position at the UN Security Council is always foiled by the US, Kamal said.
Britain, Germany and Romania abstained from the vote while the 11 other council members voted for it.
In Jordan, the pro-government daily al-Rai said the veto gave Israel a free hand to pursue its deadly operation, which has killed more than 90 Palestinians and which Israeli military sources said would continue until at least Sunday.
"The Bush administration has turned its back on international legislation and public opinion," the newspaper said in a commentary, charging that the US veto was "a green light to pursue the massacre" in Gaza.
The only concern of US President George Bush and his administration is "to protect Israel and justify its arrogance and its sickly tendency to use force", the paper said.
Al-Dustour, another leading Jordanian daily, said the US veto effectively "supports [Israeli] terrorism" against the Palestinians and criticised Washington's "blind support for Israel".
"The Bush administration has turned its back on international legislation and public opinion"
On Wednesday, Egyptian Foreign Minister Ahmad Abu al-Gheit regretted the veto and warned Israel not to see this as a "green light to continue its practices against the Palestinians".
Abu al-Gheit also urged the Palestinians to refrain from targeting Israeli civilians, arguing that this would not serve the peace process or their own cause.
His Jordanian counterpart, Marwan Moasher, said in Spain on Tuesday that efforts to secure a two-state solution with Israelis and Palestinians living side by side were "in serious jeopardy" as a result of the Israeli operations in Gaza.
The Arab Lawyers Union said Washington's decision to resort to the veto had blocked "condemnation of the Israeli butchery in the Gaza Strip", in a statement released in Cairo.
It made the US "a full partner of the Zionist entity in its attack on the Palestinian people and the implementation of its extermination plan", the union charged.