"It's a pretty good deal," he told NBC on Sunday.
He dismissed concerns put forward by skeptics about independent inspectors’ ability to verify that Iran is following the agreement.
“I think a very vigorous verification regime has been put into place," he said.
"I say, we have a deal, let's see how they implement the deal. If they don't implement it, bail out. None of our options are gone," Powell added.
He noted that, even if the deal fails in Congress, dozens of other nations who partook in the negotiations have already agreed to it, and this makes it impossible for the US to sit out.
"Even if we were to kill the deal — which is not going to happen — it's going to take effect anyway, because all of these other countries that were in it with us are going to move forward," he said.
"They're all going to be moving forward — we're going to be sitting on the sidelines," the former official stated.
The agreement is currently being reviewed by the Republican-dominated Congress and the lawmakers have until September 17 to vote on it.
President Barack Obama, Secretary of State John Kerry, Energy Secretary Ernest Moniz and other high-ranking officials have been vigorously lobbying in favor of the agreement, answering every lawmaker’s questions in person.
During his two-week vacation in Martha’s Vineyard last month, Obama spoke to over 100 lawmakers in individual or small-group settings, and even made telephone calls over the nuclear agreement, according to a White House official.
So far, 38 senators have announced that they will vote in favor of the deal, which means Democrats have enough votes to protect a presidential veto in case of an initial turn-down of the agreement; Press TV reported.