Horst Teltschik, a former security consultant to the German chancellor, says it's in Iran's interest to agree to disagree with the West. He has called for Iran to be invited to the upcoming Syria peace talks.

DW: Mr. Teltschik, the nuclear deal with Iran is still seen as very controversial - in the US, but also internationally. Israeli Prime Minister Benjamin Netanyahu has called it a "historic mistake," while "The New York Times" has said it will open new strategic options in the Middle East. What do you think?

Horst Teltschik: The domestic situation in Iran and developments outside its borders have changed dramatically. Sanctions against Iran have proven effective: the new president must spur economic development for his citizens if he wants to avoid any further demonstrations and unrest. And the developments in Syria, Iraq and Lebanon could result in substantial turbulence that won't leave Iran unaffected. In addition, the West's extensive troop withdrawal from Afghanistan is opening a new and dangerous front for the Iranians. They need to reorient themselves.

What exactly could happen in these countries that would have an influence on Iran?

In the Middle East, we have a power struggle between Saudi Arabia and the Sunnis on one side, and Iran and the Shiites on the other. This has lead to further destabilization in Iraq. In addition, there's Syria. Will Iran's closest partner, [Syrian President Bashar] Assad, survive? At the same time, there's a danger of further division in Lebanon. The worst case scenario would be that Syria, Lebanon and Iraq fail as states. And that certainly makes Iranians nervous. I believe it's in Iran's interest to find a modus vivendi with the West on the nuclear issue. And I don't rule out the possibility that they want to have the Americans invite them to participate as a partner at the Syria peace conference.