"Never trust America, NATO, and criminal regimes like Britain, France and Italy -- who for a long time divided your lands (among themselves) and plundered them," Khamenei said as he opened a two-day conference in Tehran on "Islamic Awakening" attended by several hundred guests from Arab countries.
"Be suspicious of them and do not believe in their smiles. Behind those smiles and promises lie conspiracy and betrayal," Khamenei said. "Look for solutions in ... Islam."
"Do not let your enemies dictate your plans for the future, do not sacrifice the principles of Islam before temporary interests," he said in remarks broadcast live on state television.
Iran has vocally supported most uprisings in the Arab world, with the exception of the revolt in its regional ally Syria, where it backs the regime of President Bashar al-Assad while advocating reform.
The Islamic republic has in recent months repeatedly accused the West of attempting to hijack the revolt movements in the Arab world.
Khamenei said the "ultimate goal" of the regional revolutions should be creating a new Islamic civilisation based on religion, logic, science and morals -- one which is away from Western schools of thought.
He also denounced the intervention of NATO in Libya, saying the operation had inflicted "irreparable losses" on the country through destroying its infrastructure.
"If it were not for these interventions, the Libyans may have taken longer to succeed but so many innocent people would not have been killed and the former allies of Gaddafi would not have been able to seek to interfere (politically) in this war-ravaged and oppressed country," Khamenei said.
Lebanese Hezbollah's number two Sheikh Naeem Qassem, secretary general of Palestinian Islamic Jihad, Ramadan Abdullah, and former Afghan premier and warlord Burhanuddin Rabbani are attending the meeting.