From Brownback's Website:
Iran remains the world's leading state sponsor of terrorism, supporting terrorist groups like Hamas and Hezbollah among others. These terrorist organizations are largely behind the suicide bombers in Israel and support attacks against U.S. interests in the region and U.S. forces in Iraq. Iran's influence frustrates efforts to achieve peace in the Middle East. On top of all of this, Iran's nuclear program threatens the security of Iran's neighbors and the rest of the world.