Hizbullah's leader has accused US president Barack Obama of absolute bias in favour of Israel and disregard for the dignity of Arabs and Muslims.
Sheik Hassan Nasrallah said Mr Obama has gone even farther in his military support for the Jewish state than his predecessor, George W Bush - who was reviled in much of the Arab world for his support of Israel and war on Iraq.
The remarks were Sheik Nasrallah's strongest criticism yet of the American president since Mr Obama took office almost a year ago.
Sheik Nasrallah said President Obama's earlier statements calling on Israel to freeze settlement building and then going back on that demand was a "tactic" agreed on by both Israel and the US.
Mr Obama's initial settlement demand was "an American ploy to pass the time and gain Arab sympathy," Sheik Nasrallah said, adding any "illusions" anyone had about Mr Obama being more even-handed have now collapsed.
"What we see is absolute American commitment to Israeli interests, Israeli conditions, and Israeli security ... while disregarding the dignity or feelings of the Arab and Muslims people and their nations and governments," he said in a speech broadcast to tens of thousands of supporters in a southern Beirut suburb.
Sheik Nasrallah, who is influential among supporters of his Shia group in the Arab world, also warned Israel against waging another war on Lebanon, repeating his pledge to hit back deep within Israel.
Hizbullah and Israel fought a bitter 2006 summer war that killed around 1,200 people in Lebanon and 160 in Israel before it ended with a UN-brokered cease-fire.
Sheik Nasrallah also lashed out at a major missile defence exercise staged recently by American and Israeli forces to test technology that would protect Israel from a missile attack.
US military officials have described it as the most complete air missile defence system done anywhere in the world.
"The Americans are coming, for the first time in decades and perhaps the first time since Israel's existence, to be a field partner in any confrontation that Israel might impose on Gaza, Lebanon, Syria or Iran," he said.
Sheik Nasrallah, who fears an assassination by Israel and is in hiding at a secret location, didn't address comments by Israel's army chief, Maj Gen Gabi Ashkenazi, who said on Tuesday that Hizbullah has significantly expanded its ability to strike deep into Israel, with tens of thousands of missiles that can now reach its largest cities.
He also did not comment on Israel's seizure of a ship last week carrying weapons it said originated in Iran and were destined for Hizbullah - a claim Hizbullah has already denied.