TEHRAN, Iran -- Iran's supreme leader said Wednesday that Tehran will not expand talks with the United States beyond the international negotiations over its nuclear program and predicted that Israel would not exist in 25 years.

Ayatollah Ali Khamenei's statements underscored his lingering distrust of the United States and hostility toward Israel as the U.S. Congress prepares to vote on the landmark nuclear agreement reached with Tehran in July.

U.S. President Barack Obama appears to have secured enough support from Democrats to prevent the Republican-led Congress from derailing the deal, but Khamenei's latest remarks were likely to be seized upon by critics of the agreement as proof that Iran cannot be trusted.

His remarks also appeared to quash any hopes of a broader rapprochement between Washington and Tehran, or future co-operation on other regional issues, including the two countries' shared battle against the Islamic State group.

"We approved talks with the United States about the nuclear issue specifically. We have not allowed talks with the U.S. in other fields and we will not negotiate with them," Khamenei said at a gathering of hundreds of people in a mosque in Tehran, according to his official website.

Khamenei said America remains the "Great Satan" and warned that co-operation with Washington on other issues would allow it to "penetrate" the Islamic republic.

"The Iranian nation ousted the Satan. We should not let it back through the window," he said, referring to the 1979 Islamic revolution that toppled the U.S.-backed shah.

His remarks came a day after Iran's moderate President Hassan Rouhani signalled that Tehran was ready to hold talks with world powers on ending Syria's civil war. Iran is a key ally of embattled President Bashar Assad, while the U.S. supports the rebels fighting to overthrow him.

Khamenei, who makes the final decision on major policies, also lashed out at Israel, which is staunchly opposed to the nuclear agreement. Critics of the deal say a key weakness of the agreement is that certain provisions would expire in 10, 15 or 25 years.

"Some Zionists have said that regarding the result of the nuclear deal they (Israelis) have been relieved of concerns about Iran for 25 years," Khamenei said.

"But we tell them that you will not see the coming 25 years and God willing there will not be something named the Zionist regime in the region."

Iran has long supported militant Palestinian and Lebanese groups pledged to Israel's destruction, and Khamenei and other leaders have repeatedly predicted Israel's demise.

Israel, the region's sole if undeclared nuclear-armed state, has refused to rule out a military option to prevent Iran from getting atomic weapons.

Israel and Western countries have long accused Iran of pursuing nuclear weapons alongside its civilian program, allegations denied by Tehran.