DUBAI (Reuters) - Iran's Supreme Leader Ayatollah Ali Khamenei said on Sunday the United States had created the "myth" of nuclear weapons to portray Iran as a threat, hardening his rhetoric before nuclear negotiations resume this week.

Khamenei has supported the talks but has continued to express deep mistrust of the United States. As the highest authority in Iran, the withdrawal of his support could cause the negotiations to collapse.

"They created the myth of nuclear weapons so they could say the Islamic Republic is a source of threat. No, the source of threat is America itself," Khamenei said in comments cited by the semi-official Fars news agency.

"The other side is methodically and shamelessly threatening us militarily ... even if they did not make these overt threats, we would have to be prepared," he said in an address to military commanders.

Iran and six world powers including the United States reached a framework accord on Iran's disputed nuclear programme this month and will resume negotiations in Vienna this week aiming to reach a final deal by the end of June.

Despite significant progress, the two sides still disagree on several issues, including how quickly international sanctions would be lifted under a final deal.

By Reuters