(JTA) — President Obama tamped down expectations about brokering a nuclear deal with Iran before the upcoming deadline.

“There’s still a big gap,” Obama told “Face the Nation” host Bob Schieffer on Sunday on the 60th anniversary broadcast of the CBS program. “We may not be able to get there.”

Nov. 24 is the deadline for a nuclear deal between Iran and six world powers. American negotiators in recent weeks have sounded more optimistic about achieving an agreement.

Obama said there have been “significant negotiations.”

Israel rejects any deal that allows Iran to continue enriching uranium at even minimal levels, which it is believed that a nuclear deal with Iran will include. Israel believes any enrichment capacity leaves Iran as a nuclear threshold state.

Meanwhile, Iran’s supreme leader, Ayatollah Ali Khamenei, posted Sunday on his official Twitter account a plan to eliminate Israel, or what he called the “fake Zionist regime.”

“The elimination of Israel does not mean the massacre of the Jewish people in the region,” he said.

The plan, which Khamenei believes will be palatable to the international community, calls for a referendum by “all the original people of Palestine including Muslims, Christians and Jews wherever they are.”

“Naturally, the Jewish immigrants who have been persuaded into emigration to Palestine do not have the right to take part in this referendum,” according to the nine-point plan.

Khamenei said the plan “can be properly understood by global public opinion, and can enjoy the support of the independent nations and governments.”

His plan rejects a “classical war” or an arbitration by the United Nations or other international organizations.