By Aresu Eqbali, Rory Jones and Joel Greenberg 

Iran's Supreme Leader Ayatollah Ali Khamenei on Thursday urged his country's parliament to vote on whether to implement a proposed nuclear deal with the U.S. and five other world powers, even as Israel's prime minister vowed to continue lobbying against the pact.

The sharply divergent positions, from two rivals on opposite ends of the nuclear deal, illustrate how the contentious pact has stirred up political challenges for leaders far beyond the U.S.

In considering the deal, Mr. Khamenei must placate Iran's conservative hard-liners, who oppose closer ties with the U.S. after decades of avowed distrust between the two countries, and moderates who support a rapprochement with the Western world. Mr. Khamenei, who has the final say over most matters of state in Iran, threatened to torpedo the deal if economic sanctions against the country aren't lifted entirely, rather than merely suspended.

The remarks, published by state news agency IRNA, come a day after the White House secured enough congressional support to all but ensure the deal's implementation.

"If the sanctions are not removed, there will be no deal," he said. "I don't have any advice to the parliament about how to examine it, approval or disapproval."

Both the country's Parliament and the Supreme National Security Council, a body over which Mr. Khamenei has control, must sign off on the nuclear deal, before it falls to Mr. Khamenei to ultimately decide on whether it moves ahead.

Separately, Israeli Prime Minister Benjamin Netanyahu will keep up his campaign against the nuclear deal with Iran, despite his failed lobbying effort to scuttle it in the U.S. Congress, a senior Israeli official said Thursday.

"Prime Minister Netanyahu has a responsibility to speak out about the grave dangers the Iran deal presents to Israel, the region and the world, and he will continue to do so," said the senior Israeli official, who spoke anonymously because he wasn't authorized to comment publicly.

Mr. Netanyahu said he believed the American public shared his views on the Iranian threat.

"An overwhelming majority of the American public sees eye to eye with us on the danger posed by Iran, and it's important to instill in American public opinion in the coming decade, perhaps beyond, the fact that Iran is the enemy of the United States. It openly declares that," he said. "And Israel is an ally of the United States. This understanding has important implications for our security."

The Israeli response came after President Barack Obama succeeded in securing enough votes in the Senate to uphold his expected veto of a Republican-backed resolution to reject the agreement.

Mr. Netanyahu has been a vociferous opponent of the accord reached in July between world powers and Iran to curb its nuclear program, arguing that it leaves Tehran with the capacity to produce nuclear weapons that could destroy Israel.

He has asserted that sanctions relief provided by the deal will help Iran fund Islamist militants throughout the Middle East.

A deal with powers, including the U.S., U.K., France, Germany, Russia and China, will have far-ranging economic repercussions for Iran, limiting its nuclear program in exchange for the easing of sanctions that have crippled its economy.

President Obama clinched enough support in the Senate to all but ensure that the U.S. implements a deal with Iran. His administration secured the backing of 34 senators in the Democratic caucus, the minimum number required to guarantee the advancement of the deal.

The endorsement means that even if Congress passes a resolution rejecting the agreement, Mr. Obama has enough votes in the Senate to veto the decision.

After the deal's announcement in July, Mr. Khamenei said Iran wouldn't surrender to excessive demands and vowed not to change its policy of supporting regional allies regardless of their frosty relations with the U.S.

Iran has kept up ties with the regime of Syrian President Bashar al-Assad and is a big backer of the Lebanese militant group Hezbollah.

Critics of Mr. Netanyahu, meanwhile, called Mr. Obama's success in Congress a resounding defeat for the prime minister, whom they accused of souring relations with the White House while waging a vigorous lobbying drive for congressional rejection of the Iran deal.

"Netanyahu failed completely in his campaign," opposition leader Isaac Herzog told Israel Radio. "He raised the bar so high that it exacted a price, and the price is a political price in the United States."

Write to Rory Jones at rory.jones@wsj.com

(END) Dow Jones Newswires

September 03, 2015 14:35 ET (18:35 GMT)