Sen. Bob Corker cautioned against a nuclear deal because Iran will "cheat by inches."

The Senate Foreign Relations Committee Chairman added that Iran desires nuclear weapons no matter what diplomatic deal is reached.

"We know they were building a bomb, we just don't know how far along they were," he said on NBC's "Meet the Press" Sunday. He said he is concerned about a deal because we have to make sure it is "verifiable" that they are no longer working on nuclear weapons.

Reports surfaced Sunday that a provisional deal curbing Iran's nuclear program in exchange for sanctions relief is to be announced by Monday — the latest deadline for a deal. Negotiators from Iran, the U.S., Britain, China, Germany, France and Spain have missed the four previous deadlines.

Corker believes the delays are for the best.

"I am glad they are taking their time. I actually think the deadline was working in Iran's favor," Corker said of the original June 30 deadline.

If a final deal is reached by Monday, Congress has 60 days to review it. Corker said that his fellow lawmakers will do what is best for both the U.S. and the greater international community if and when the time comes to review the deal.

"We have a responsibility on this. The world's eyes are going to be on Congress once this comes over," he said of the deal. "At the end of the day, people are going to vote their conscience."