Iranian Supreme Leader Ayatollah Ali Khamenei said it would be an "unforgivable mistake" to negotiate with Israel, days after Saudi Arabia's crown prince for the first time said Israelis are entitled to live peacefully on their own land.
Although Khamenei, in remarks carried on his website on April 4, did not specifically mention Saudi Prince Muhammad bin Salman's statement, he made it clear Tehran opposes an apparent thaw in ties recently between Israel and the Saudis.
The heir apparent to the Saudi throne, besides telling The Atlantic magazine that Israelis have a right to live peacefully on their own land, recently authorized direct Air India flights between New Delhi and Tel Aviv via Saudi airspace. Saudi Arabia had previously banned flights over its territory bound for Israel.
"Movement toward negotiation with the cheating, lying, and oppressive regime [of Israel] is a big, unforgivable mistake that will push back the victory of the people of Palestine," Khamenei said.
The Iranian leader said it is the "religious duty" of all Muslims to support Palestinian resistance movements, and he pledged continued Iranian backing for the Palestinian Islamist group Hamas.
Saudi Arabia still does not formally recognize Israel. Riyadh has long maintained that normalizing ties with Israel hinges on an Israeli withdrawal from Arab lands captured in the 1967 Middle East war -- territory Palestinians seek for a future state.
But in November, an Israeli cabinet member disclosed he had covert contacts with Saudi Arabia, a rare acknowledgment of long-rumored secret dealings which Riyadh still officially denies.
Analysts say the improving relations between the two one-time enemies is likely motivated by what both see as a common threat from Iran.
Khamenei issued his statement in reply to a letter he recently received from Hamas chief Ismail Haniya, which criticized the support of Arab governments in the region for the United States.
Hamas, which has vowed to destroy Israel, dominates the small coastal strip of Gaza, where this week at least 17 Palestinians were killed in clashes with Israeli security forces.
In his statement, Khamenei called on the people of Muslim countries to join Hamas in defeating Israel.
Separately on April 4, Israeli Prime Minister Benjamin Netanyahu denounced a statement by Iranian President Hassan Rohani that the United States and Israel support "terrorists" in Syria.
Iran, Syria, and Russia often refer to their opponents in Syria's seven-year civil war as "terrorists." Rohani made the remark at a summit with Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan in Ankara on April 4.
"If Rohani is unaware of the terrorist and sabotage activities conducted daily by the Iranian Quds Force in Syria, Israel can provide him with an update," Netanyahu said.
At the summit, Rohani also said he doubts U.S. President Donald Trump will soon withdraw U.S. troops from Syria, as the American president has vowed to do recently.
Netanyahu expressed his concern about a possible U.S. withdrawal from Syria in a phone conversation with Trump late on April 3, saying that would allow Iran and allied Hizballah militias to gain an even stronger foothold in the country, U.S. and Israeli officials said.
Israeli Defense Minister Avigdor Liberman told Israel's Army Radio that Israel will not allow Iran to expand its presence in the neighboring country, regardless of what the United States does.
“They are building settlements in Syria, intend on settling there, and are talking about the infrastructure they want to build,” the defense minister said. “This is categorically unacceptable to us, and we will not accept it.”