US Democratic presidential hopeful Hillary Clinton says she would not hesitate to launch a war against Iran should the Islamic Republic violate the nuclear agreement.

“I will not hesitate to take military action if Iran attempts to obtain a nuclear weapon,” Clinton told a Washington think-tank on Wednesday.

"The Iranians and the world need to understand that we will act decisively if we need to," she said. "As president, I will take whatever actions are necessary to protect the United States and its allies."

She made her case in a speech at the Brookings Institution in Washington DC as the US Senate is set to begin its debate on the Joint Comprehensive Plan of Action (JCPOA) concluded by Iran and the P5+1 group of countries -- the US, Britain, France, China, Russia plus Germany -- in the Austrian capital, Vienna, on July 14.

“We should anticipate that Iran will test the next president, “she said. “They'll want to see how far they can bend the rules."

Clinton further said, “I don’t see Iran as our partner in implementing the agreement. I see Iran as our subject in implementing the agreement.”

She also defended the agreement, stressing that rejecting the accord by the Congress would lead to international isolation for the US.

"Several Republicans boast they'll tear up this agreement in 2017," she said. "That's not leadership, that's recklessness."

The Republican-dominated Congress is reviewing the nuclear agreement and has until September 17 to vote to either approve or disapprove of it.

Under the accord, Iran has been recognized by the United Nations as a nuclear power and will continue its uranium enrichment program, but some restrictions will be placed on Iran’s nuclear program in exchange for the removal of sanctions.