"They've had an effect on Iran's currency, they've hurt the living standards, they've hurt the economy," he said.
"And it's not an unreasonable assumption that they would push the leadership towards a negotiated outcome here."
The effectiveness or otherwise of sanctions is certainly a subject for debate, but in this respect Mr. Carr is not saying anything particularly controversial. The official position, and indeed the hope of most interested parties is that sanctions could cause the Iranian leadership to reconsider its position.
The problem with Mr. Carr's position is enshrined in this statement, referring to the threat of military strikes:
"It should be off the table as we persist with sanctions, and persist with seeking a negotiated settlement," Senator Carr told Sky News on Thursday.
Now, nobody - not Israel, not the United States and certainly not Australia - actually wants to see a military intervention in Iran. President Obama has made that absolutely clear in his public statements. But to suggest that the military option should be taken off the table is another thing entirely.
The threat of military strikes is a powerful negotiating tool, if used properly. To rule that option out entirely would simply signal to the Iranian leadership that it can continue to misbehave without fear of serious retribution. Mr. Carr, as a supposedly deep thinker, must surely understand that by removing the spectre of military action we would be weakening our own position in negotiations with Iran.
There is also a connected lesson for the American President here: threats do not work unless the recipients believe that you may actually follow through. Iran cannot think that we are bluffing - even if we are.