George Will on Iran GDP and U.S. Defense Budget

On ABC’s This Week, George Will may have explained why the Federal budget has such a large deficit. He claimed that Iran’s GDP was only one-third of Donald Rumsfeld’s defense budget. According to this source, Iran’s GDP in 2005 was $561.6 billion. Was our Federal defense spending really around $1.7 trillion? This source defense spending in 2005 was $589.3 billion. Who to trust?