Secretary of State John Kerry on Sunday defended the nuclear deal with Iran as less than perfect, but a chance to stop the country's efforts to build nuclear weapons.

"This negotiation is not the art of fantasy or the art of the ideal," Kerry said on ABC's "This Week." "It's the art of the possible, which is verifiable and clear in its capacity to be able to make Israel and the region safer."

But GOP lawmakers were mostly critical of the agreement and said Congress will be closely monitoring the deal and "weigh in," to ensure the short-term deal, which leaves intact Iran's 19,000 nuclear centrifuges, doesn't become the final agreement.

Six major countries and Iran agreed to a deal Saturday in Geneva that involves lifting about $7 billion worth of sanctions against Iran in exchange for the country taking steps to curb its nuclear program.

President Obama praised the deal as "an important first step," toward securing a larger agreement with Iran that would end the possibility of the country ever building a nuclear weapon.

But critics, including Israeli Prime Minister Benjamin Netanyahu, said the agreement is largely cosmetic and does nothing to quell the threat that Iran is working on nuclear weapons that they can use to threaten the region.

"What was concluded in Geneva last night is not a historic agreement, it's a historic mistake," Netanyahu said after the deal was announced.

Kerry told ABC that the deal is solid, and will include daily inspections of nuclear sites in Iran, and a the destruction of uranium, but he acknowledged it will not dismantle the centrifuges.

"That's correct," Kerry acknowledged. "That's the next step."

Kerry added, "You can't always start where you wind up."

He said the deal involves using the next six months negotiating for the dismantling of the centrifuges, during which time they will not be able to expand the program.

Without the deal, Kerry said, "they progress" in producing more centrifuges in and further enriching uranium, while countries argue over an agreement.

But Sen. Saxby Chambliss, R-Ga., who also appeared on "This Week," wants to increase sanctions against Iran, pointing to the endless nuclear talks with North Korea and lifting of sanctions there that yielded no agreement while the country ended up building a nuclear bomb.

The agreement with Iran does not specifically prevent the country from continuing to enrich uranium.

"They still have that capability," Chambliss. "Nothing in what Secretary Kerry just said moves us in the direction of preventing Iran from developing a nuclear weapon."

Sen. Bob Corker, R-Tenn, appearing on "Fox News Sunday," said Congress will closely monitor the deal over the next six months.

"There is bipartisan skepticism here."

Corker said he believes Iran may be taking advantage of the United States which he said has been soft on nuclear proliferation under the Obama administration.

"They do view this administration as weak," Corker said. "And from their standpoint they see this as their window of opportunity to negotiate with an administration that has shown they do not have the intestinal fortitude other administrations have had."

But Kerry, on "This Week," used compelling numbers to make the case that the deal does, in fact, slow Iran's progress toward building a bomb.

During the administration of President George W. Bush, Kerry noted, Iran had 164 centrifuges. A decade has since passed without a nuclear deal, giving the country time to build its current inventory of 19,000 centrifuges.

"You cannot sit there and pretend that you're just going to get the thing you want while they continue to move towards the program that they've been chasing," Kerry said.

Sen. Ben Cardin, D-Md., praised the deal, but said Congress needs to be ready to impose bigger sanctions if Iran doesn't comply with the deal.

"We are very concerned as to whether Iran will live up even to theses commitments," Cardin said. "This is a first step."