Israeli Prime Minister Benjamin Netanyahu, in a dramatic speech to the United Nations, employed a simple diagram to hammer home his plea that the international community set a "clear red line" over Iran's nuclear program -- warning that a nuclear-armed Iran would be tantamount to a nuclear-armed Al Qaeda.

Netanyahu claimed Thursday that Iran would have enough enriched uranium to make a nuclear bomb by next summer. His remarks before the U.N. General Assembly amounted to an appeal to the U.S. and other nations to join Israel in drawing a line that Iran cannot cross without risking a military response.

Netanyahu argued that nothing less than the "security of the world" is at stake.

"The red line must be drawn on Iran's nuclear enrichment program," Netanyahu said. "I believe that faced with a clear red line, Iran will back down."

The prime minister displayed a "diagram" showing a crudely drawn sketch of a bomb, divided into sections representing the three stages of uranium enrichment. Using a marker, Netanyahu drew a red line before the end of the second stage.

"Red lines don't lead to war, red lines prevent war," he said. "Nothing could imperil the world more than a nuclear-armed Iran."

Netanyahu warned that it would be a "dangerous assumption" to think Iran could be deterred like the former Soviet Union.

"Imagine their long-range missiles tipped with nuclear warheads, their terror networks armed with atomic bombs -- who among you would feel safe in the Middle East?" he said.

The remarks were a challenge to the Obama administration, which has sought to hold off Israeli military action, which could result in the U.S. being drawn into a chaotic conflict with elections looming. Though Obama has tried to wield economic sanctions and international diplomatic efforts to make progress with Iran, Netanyahu claims those efforts have failed. Israeli leaders have issued a series of warnings in recent weeks suggesting that if Iran's uranium enrichment program continues it may soon stage a unilateral military strike, flouting even American wishes. On Sunday, Iranian leaders suggested they may strike Israeli preemptively if they feel threatened.

The issue has led to tensions between Obama and Netanyahu. That perception was heightened after Obama did not make plans to meet with the prime minister this week during his visit to New York -- though Secretary of State Hillary Clinton was expected to meet with him Thursday night, and Obama is planning a phone call Friday. Mitt Romney, meanwhile, said in a statement Thursday that he joins Netanyahu's "urgent call" to prevent a nuclear-armed Iran.

Obama briefly addressed the Iranian threat during his remarks Tuesday to the United Nations, saying the U.S. "will do what we must" to prevent Iran from gaining a nuclear weapon.

Netanyahu said Thursday "I very much appreciate the president's position."

Netanyahu began his U.N. address with an implicit rebuke to Iran's Mahmoud Ahmadinejad, telling the history of the Jewish people's ties to the land of Israel and vowing that they would remain there.

"Throughout our history the Jewish people have overcome all the tyrants who sought our destruction," he said. "The Jewish people have come home. We will never be uprooted again."

A few hours before Netanyahu flew to the U.S., Ahmadinejad spoke at length about his vision for a "new world order" during his speech at the U.N. His speech on Wednesday happened to fall on Yom Kippur, the most sacred day on the Jewish calendar, devoted to fasting, prayer and introspection.

Netanyahu issued a statement condemning the speech soon after the fast ended. "On the day when we pray to be inscribed in the book of life a platform was given to a dictatorial regime that strives, at every opportunity, to sentence us to death," Netanyahu said.

At the U.N. on Thursday, Netanyahu also said he wants a "durable peace" with the Palestinians - but rebuked Palestinian Authority President Mahmoud Abbas for his remarks just moments earlier.

"We won't solve our conflict with libelous speeches at the U.N.," Netanyahu said.

Earlier, Abbas had said he will seek to apply to the General Assembly for nonmember status as a sovereign country while cautioning that the expansion of Israeli settlements hurts chances for a two-state solution.

"Despite all the complexities of the prevailing reality and all the frustrations that abound, we say before the international community there is still a chance -- maybe the last -- to save the two-state solution and to salvage peace,'' Abbas said.

Palestinian officials said the bid is likely to be submitted on Nov. 29. The effort was not intended to pose a threat to Israel, Abbas said.

"We are not seeking to delegitimize Israel, but rather establish a state that should be established: Palestine," Abbas said.

He also warned the assembly that Israel is promising a "new catastrophe" if it continues with current policies in the West Bank.

The Associated Press contributed to this report.