Mohammad Bagher Ghalibaf's remarks came as reports emerged that US President Donald Trump had sent a tougher peace proposal back to Iran, and underlined the rift that the parties still need to close.

Any tweaks to the draft could further delay an agreement to formally end the Middle East war and reopen the Strait of Hormuz after weeks of fraught negotiations marked by sharp rhetoric and occasional flare-ups of violence.

Iran was already in talks with the United States about the fate of its nuclear programme in February when the US and Israel launched air and missile strikes that wiped out much of the Islamic republic's senior leadership.

And, while Tehran has long insisted that its nuclear programme is for purely civilian ends, the United States and its Western allies suspect it aims to develop a weapon.

The New York Times and Axios reported on Saturday that Trump had sent back a "tougher" new framework to be considered by Iran, though details remain unclear.

Trump has said his priorities include stopping Iran from developing any nuclear weapon and reopening the Hormuz shipping lane, which Iran has blockaded since the war began.

"The one guarantee that I have to have is that there will be no nuclear weapons. They've agreed to that, and it was very interesting," he told his daughter-in-law Lara Trump in an interview on her Fox News show.

Tehran, however, has previously cast doubt on Trump's assertions and the sides remain far apart on key issues.

"We will not approve any agreement until we are certain that the rights of the Iranian people have been upheld," Ghalibaf said in a video broadcast on state television.

According to the Tasnim news agency, exchanges on the text "are ongoing, with both parties regularly proposing amendments".

Iranian Foreign Minister Abbas Araghchi, meanwhile, said that "until a clear conclusion is reached... everything that is being said now is speculation", according to state TV.

Iran has said it needs the release of $12 billion in frozen assets before engaging in substantive talks on its nuclear programme, dismissing earlier Trump comments that its enriched uranium stockpile would be destroyed as "baseless", according to Iranian media.

- Flare-ups -

One of Washington's stated war aims was the destruction of Iran's ballistic missile programme, with General Dan Caine -- the top US military officer -- estimating in April that more than 80 percent of its missile facilities had been struck.

But CNN reported on Sunday that an analysis of satellite imagery showed Tehran has since been able to excavate 50 out of 69 tunnel entrances hit by US strikes at 18 underground missile sites.

Though daily strikes throughout Iran and the Gulf halted after Tehran and Washington agreed to a temporary ceasefire in April, there have been sporadic attacks.

Iran's Revolutionary Guards had shot down a US military drone "about to enter Iranian territorial waters", Iran's state broadcaster IRIB reported, though Washington has not confirmed the incident.

Trump is under pressure to secure a deal that would lift competing US and Iranian blockades around the Strait of Hormuz that have strangled a vital route for global oil supplies.

After Trump said Iran would charge "no tolls" on ships passing through the strait under any deal, Iranian news agency Fars cited sources saying "no such clause" existed.

Iran's ISNA news agency on Saturday quoted lawmaker Alireza Salimi as saying a plan for Iranian "management and sovereignty" over the strait -- including imposing "administrative fees" -- would soon go before parliament.

- Lebanon front -

Tehran has insisted that any peace deal include Lebanon, where fierce fighting continues, with Beirut accusing Israel of pursuing a "scorched-earth policy" as it expands operations against Iran-backed Hezbollah.

A truce between Israel and Hezbollah formally began on April 17 but it has never been observed, with both sides accusing each other of violating it.

The UN Security Council will hold an emergency meeting Monday on the widening Israeli offensive following its capture of the strategic medieval castle of Beaufort, diplomatic sources told AFP.

Smoke billowed from the surrounding area Sunday as its flag was seen by AFP above the castle, which Israel famously used as a base during their previous two-decade occupation.

Israeli Prime Minister Benjamin Netanyahu called the retaking of Beaufort "a dramatic shift".

Hezbollah lawmaker Hassan Fadlallah said the castle "was not a military site", adding the raising of the Israeli flag there "should provoke the feelings of every loyal patriot".

burs-smw/amj

THE NEW YORK TIMES COMPANY