Iranian President Mahmoud Ahmadinejad has written a letter to U.S. President Barack Obama, calling on him to cooperate with the Islamic Republic, CNN reported on Friday citing the Iranian Republic News Agency (IRNA).

"Obama has only one way to remain in power and be successful," Ahmadinejad reportedly said in a speech earlier this week. "This way is Iran."

Obama has been pushing fellow members of the UN Security Council, particularly Russia and China, to support enacting a tougher package of sanctions on Iran over its nuclear program.

Washington fears Iran's nuclear program will allow Tehran to develop nuclear weapons. Iran denies any such intention and says it only wants to generate electricity.

Ahmadinejad said that it is not Iran that faces isolation from the world but rather the U.S. that finds itself in that situation.

"Once [the U.S. was] at the height of glory," he said. "Now they are collapsing. They have many economic and cultural problems. They have security problems in the world and their influence in Iraq and Afghanistan is vanishing."

In 2006, Ahmadinejad wrote an 18-page letter to then-President George W. Bush discussing religious values, history and international relations. That was the first publicly acknowledged communication between leaders of the two nations since 1980 just after the Islamic Revolution in Iran that overthrew the Shah.

In 2008, Ahmadinejad sent a congratulatory message to Obama after he won the presidency.