Speaking in New York on Friday before members of the Council on Foreign Relations think tank, Kerry declared there are "no alternatives" to the nuclear agreement
the United States and five other world powers struck with Iran.
A clear focus in Kerry's message on Friday was his past and continuing support for Israel, even recalling his 100% voting record for Israel during his time as senator.
With the deal, Kerry said, "I believe Israel is safer, I believe the region is safer, I think the world is safer," but he warned that if the deal isn't adopted, "friends in Israel could end up being more isolated and more blamed."
Relations between the longtime ally nations are obviously tense.
Referencing the 2012 United Nations General Assembly, in which Israeli Prime Minister Benjamin Netanyahu held up a drawing of a bomb, Kerry said, "We've seen the Prime Minister with a cartoon of the bomb at the U.N. ... But what's happened? What has anyone done about it? Anybody got a plan to roll it back? Anybody got a plan that's viable beyond bombing for one or two days or three days that might slow their program down for two years or three years?"
Michael Oren, Israel's former ambassador to the United States and a member of the Knesset, responded to Kerry's remarks, saying that a rejection of the deal by lawmakers would come "exclusively on the basis of U.S. interests."
"The threat of the secretary of state who, in the past, warned that Israel was in danger of becoming an apartheid state, cannot deter us from fulfilling our national duty to oppose this dangerous deal," Oren said.
Oren was referring to last year's prediction by Kerry of an apartheid situation
if Israel and the Palestinians fail to agree on a two-state solution for their decades-long conflict.
On Friday, Kerry was firm and passionate in replying to critics of the deal in Congress.
"Do you think the ayatollah is going to come back to the table if Congress refuses this and negotiate again? Do you think they're going to sit there and other people in the world are going to say, 'Hey let's go negotiate with the United States. They have 535 secretaries of state,'" Kerry quipped.
"I mean, please. I would be embarrassed to go out."
Reneging on the agreement would compromise not only the developing relationship with Iran, but also the future of American relations with other countries, Kerry said.
"If the United States Congress unilaterally walks away from this arrangement that we have reached, we go right back to square one," Kerry said. "Iran is enriching, we have no inspections, we have no ability to know what they're doing. We don't roll back their program, we're right back where we were and we're going to head to conflict."
Friday's event came a day after Kerry was grilled in Washington
by a panel of senators, including several Democrats.
Congress has the ability to vote against the agreement at the end of a 60-day review period. President Obama has said he will veto a vote against the deal, but would need enough Democrats supporting him to sustain the veto.
Many critics have questioned what happens when the deal expires in 15 years.
"This is not a question of what happens in 15 years or 20 years," Kerry said. "This is a question of what happens now, tomorrow, if we don't accept this deal. Because Iran will go right back to its enrichment."