TEHRAN - Iranian President Hassan Rouhani urged Muslims worldwide on Saturday to unite against the United States and assured Saudis they were "brothers" who had nothing to fear from Tehran.

US President Donald Trump abandoned a landmark 2015 nuclear deal between major powers and Tehran in May and has since reimposed crippling unilateral sanction.

"What the United States wants of (the Middle East) today is enslavement," Rouhani told an Islamic unity conference in Tehran.

Instead of "rolling out the red carpet for criminals," Muslim governments should unite against the United States and "the region's cancerous tumour", Israel, he said.

Rouhani urged Shiite Iran's Sunni rival Saudi Arabia to end its dependence on "insulting" US military aid.