Iran has vowed to retaliate against any attack, after Israeli Prime Minister Benjamin Netanyahu called on the world to draw a "clear red line" on Tehran's nuclear program.

Iran’s U.N. ambassador Eshagh al-Habib accused Netanyahu of making “baseless allegations” against Tehran, which insists its nuclear program is for peaceful purposes. World powers say Iran is seeking to develop nuclear weapons.

On Thursday, Netanyahu told delegates at the U.N. General Assembly that time was running out for the world to stop Iran. He used a drawing of a bomb to explain that a “red line” must be drawn before Iran completes the second stage of nuclear enrichment necessary to make a bomb.

Earlier this week , U.S. President Barack Obama said the U.S. will do what is necessary to prevent Tehran from obtaining a nuclear weapon but he did not give Iran any ultimatums. U.S. Secretary of State Hillary Clinton met with Mr. Netanyahu late Thursday. Officials did not provide any details of the talks.

Also Thursday, representatives of the P5+1 group of nations – the United States, Russia, China, Britain, France and Germany – met on the sidelines of the U.N. General Assembly to discuss efforts to resume nuclear talks with Iran. A State Department official said the group “remains completely unified in wanting to get the Iranians to consider and to address the concerns of the international community, and that the P5+1 is completely united in ensuring that Iran does not acquire a nuclear weapon.”