Iran''s supreme leader Ayatollah Ali Khamenei urged world Muslims on Wednesday to join the Palestinian "resistance" against Israel, but his call was dismissed by US Secretary of State Hillary Clinton and Palestinian president Mahmud Abbas.

"The only way to save Palestine is resistance," Khamenei said in an address to a global summit organised by Tehran in aid of the war-battered Gaza Strip and the Palestinians.

"Support and help to Palestinians is a mandatory duty of all Muslims. I now tell all Muslim brothers and sisters to join forces and break the immunity of the Zionist criminals."

Iran''s top military commander Mohammad Ali Jafari also declared that the Islamic republic has long-range missiles that can reach Israeli nuclear sites.

"Today the Islamic republic has missiles with a range of more than 2,000 kilometres (1,250 miles) and... all the land of the Zionist regime, including its nuclear installations, is within our range," Jafari, the head of Iran''s Revolutionary Guards Corps, told the ISNA news agency.

He said the Islamic republic could "firmly retaliate" if it was attacked by Israel, which considers Iran its biggest threat.

Khamenei said any negotiations to solve the Israel-Palestinian conflict were fruitless, adding that the United States and Britain committed the "crime of creation and supporting this cancerous tumour (Israel)."

"Even the new president of the United States who came to power with the motto of changing the (George W.) Bush administration''s policies talks about unconditional commitment to secure Israel. This is defending terrorism by a government."