The full interview will air on Cavuto's show Wednesday at 8 p.m. on the Fox Business Network.
The two most important issues the U.S. should keep an eye on, the George W. Bush appointee added, are Iran’s nuclear program and Iran’s relationship with Syria.
Syria’s other allies, Russia and China, have warned the U.S. in the last day that the administration must abide by international law, and get approval from the United Nations Security Council. Russia said, otherwise, an attack would have "catastrophic consequences."
Asked if Rumsfeld thinks Russia and China would act on their threats, he said, “Well, it's hard to know. I mean there's no question that each of those two countries, the People's Republic of China and Russia, have leaders that are fundamentally opposed to our values and our interests.”
Rumsfeld also said that Secretary of State John KerryJohn KerryDepleted Dems look to Senate for 2020 nominee Voters want to drain the swamp? They can start with Louisiana GOP As Congress adjusts to Trump, Iran put under the pressure it deserves MORE “has been dealt a pretty bad hand” as a result of President Obama’s and former Secretary of State Hillary ClintonHillary Rodham ClintonFeinstein after dinner with Clinton: She has 'accepted' her loss Sanders: Trump is 'a pathological liar' Clintons remember John Glenn as a 'uniquely American hero' MORE’s decisions over the last four years.
Rumsfeld stepped down from his post as Defense secretary in 2006.