"I'd just walk away. It just amazes me that we don't, quite frankly," Graham said on Wednesday.
"I think this deal is deteriorating before our eyes. … If something doesn't change this is a disaster in the making,” he added.
The Republican senator made the comments while Washington and its negotiating partners are holding the nuclear talks with Iran in the Austrian city of Vienna to reach a comprehensive deal.
The two sides are working to finalize the text of a possible deal over Tehran’s nuclear program by the end of this month.
The Obama administration’s critics have repeatedly denounced the talks, calling on the US president to stop the negotiations.
Senator Roy Blunt, the vice chairman of the Senate Republican conference, said on Wednesday that “using the term 'negotiation' is a stretch.”
"Two years ago, we said things that we would insist on. Two years later, none of those things appear to be things that are still being discussed in these Iranian so-called negotiations,” he said from the Senate floor.
Republican Senator Ron Johnson also claimed that the Obama administration would not be able to get a "good deal" with Iran.
"I think a deal at this point would be very destabilizing. It would not be a good deal," he said.
The US State Department announced on Wednesday that Secretary of State John Kerry is set to travel to Vienna on Friday for the nuclear talks.
Meanwhile, five former Obama advisers warned the administration about signing a potential deal with Tehran.
In a letter to Obama, they said the deal “may fall short of meeting the administration’s own standard of a ‘good’ agreement.”
“Most of us would have preferred a stronger agreement,” said the letter. The agreement “will not require the dismantling of Iran’s nuclear enrichment infrastructure.”
The letter that was given to the White House and State Department on Wednesday was signed by Dennis Ross, an adviser on Iran and the Middle East in Obama's first term.
Former CIA director David Petraeus, longtime State Department proliferation expert Robert Einhorn, former vice chairman of the Joint Chiefs of Staff Gen. James Cartwright and Obama’s former chief adviser on nuclear policy Gary Samore also signed the letter.