The ties between the two nations have unravelled ever since President Trump pulled itself out of an Iran nuclear deal in which the latter had agreed to curb its nuclear programme in return of lifting of international financial sanctions.
The sanctions imposed on Tehran this week have already led banks and many companies around the world to scale back dealings with Iran. Companies doing business with Iran will be barred from the United States, President Donald Trump has said.
The Kurdish regional government proposed on Wednesday an immediate ceasefire, a suspension of the result of last month's Kurdish independence vote and "starting an open dialogue with the federal government based on the Iraqi Constitution".
"You (the United States) and your agents are the source of instability in the Middle East ... who created Islamic State? America ... America's claim of fighting against Islamic state is a lie," Khamenei said in a meeting with high-ranking Iranian officials.
"The turbulent state of the region and the world and the international adventurism of oppressors and their vassals have confronted the Islamic Iran with conditions more complicated than before," said a message from Khamenei.