The historic deal reached between six world powers and Iran to curb its nuclear program achieved its goal, and was never intended as a panacea that would reform the Islamic republic, President Obama said on Wednesday.

Rejecting the deal based on the rationale that it does not solve all problems associated with Iran's behavior "defies logic," Obama said during a press conference at the White House. "It makes no sense; and it loses sight of what was our original No. 1 priority, which was making sure they don't have a bomb," he said.

The mission was always preventing Iran from making or obtaining a nuclear weapon, Obama said. "This has been a Democratic priority, this has been a Republican priority, this has been [Israeli] Prime Minister [Benjamin] Netanyahu's priority," and this deal "achieves that goal," he added.

"But we have always recognized that ... Iran still poses challenges to our interests and our values, both in the region and around the world," Obama continued. He said the United States will continue working with regional partners, such as Israel and the Gulf States, to thwart Iran's support of groups such as Hezbollah and its effort to foment instability in places such as Yemen.

"My hope is that building on this deal we can continue to have conversations with Iran that incentivize it to behave differently ... to be less aggressive, less hostile, to operate the way we expect" peaceful nations to act, he said. But Obama added, "we're not counting on it."

Finalizing the accord was never "contingent" on Iran changing its ways, he explained. But after implementation, it will be easier to check Iran's "nefarious activities and push back" against undesirable behavior, he said.

He underscored that the arrangement is not a re-establishment of diplomatic ties, like his overture to Cuba is, but it does give the U.S. a way to engage with Tehran on issues such as Syria, Iraq and Yemen.

China, France, Germany, Great Britain, Russia and the U.S. all hope that the new relationship will lead Iran to change its way "but we're not betting on it," Obama said.Beyond countering critics' claims, Obama challenged them to come up with a better way to curb Iran's nuclear weapons program.

"And for all the objections of Prime Minister Netanyahu or, for that matter, some of the Republican leadership that's already spoken, none of them have presented to me or the American people a better alternative," Obama said.

"If 99 percent of the world's community and the majority of nuclear experts look at this thing and they say 'this will prevent Iran from getting a nuclear bomb,' and you are arguing either that it does not or that even if it does, it's temporary, or that because they're going to get a [financial] windfall of their accounts being unfrozen that they'll cause more problems, then you should have some alternative to present," he countered.

Obama said the bottom line is that there are only two ways to check Iran's nuclear ambitions: his way through diplomacy, or through war.

He implored detractors to first read the entire 100 page-plus accord, which includes five annexes, before assailing it. Then "explain specifically where … this agreement does not prevent Iran from getting a nuclear weapon," he said, adding "and why they're right and" nuclear experts and "the rest of the world is wrong, and then present an alternative."