Ayatollah Ahmad Jannati, one of the leading figures in Iran's Islamic regime, has openly called on Muslim countries to give weapons to Lebanon's Hezbollah.
Jannati, who heads the Guardian Council, a powerful political watchdog in Iran, said: "Muslim countries are expected not to deny Hezbollah and the Lebanese any kind of help, especially weapons, medicine and food."
"I request Muslims to give Hezbollah political and financial help as well as publicity, as this is a religious duty."
The comments mark a break with Iran's usual position, which emphasises "moral support" only for the Shia movement.
Iran regularly denies Israeli and Western allegations that it finances and arms the movement.
Iran's foreign minister has met his French counterpart in Beirut as both countries called for a ceasefire to end fighting in Lebanon.
Manouchehr Mottaki said: "Iran stresses the need for an immediate halt to the aggression launched by the Zionist entity on Lebanon."
Philippe Douste-Blazy, the French foreign minister, also called for a halt to the fighting.
Mottaki criticised the UN Security Council's failure to stop the crisis.
He said: "The public opinion in the Islamic world and the international community are daily and frankly condemning the Israeli attacks on Lebanon, while we see international organizations are keeping silent."
Mottaki also held talks with the Lebanese foreign minister Fawzi Salloukh.
It was the first visit by an Iranian official to Lebanon since fighting broke out between Israel and Hezbollah fighters three weeks ago.
The Iranian minister arrived over land from neighbouring Syria, border officials said.
It was not immediately known if he planned to meet Hezbollah's leader Sheik Hassan Nasrallah as he traditionally has done on past visits to Lebanon.
Nasrallah has gone underground since fighting in Lebanon broke out three weeks ago.
Israeli aircraft have destroyed his residence and office in south Beirut, but he has since given televised speeches.