President Obama admitted Tuesday in a broadcast interview that his nuclear agreement with Iran only delays Tehran from eventually acquiring a weapon, which could come immediately after Year 13 of the agreement -- leaving the problem for future presidents.

Obama made the comments about Tehran's so-called "breakout time" in an interview with NPR News that aired Tuesday morning. The president was attempting to answer the charge that the deal framework agreed upon by the U.S., Iran, and five other nations last week fails to eliminate the risk of Iran getting a nuclear weapon because it allows Tehran to keep enriching uranium.

Obama said that Iran would be capped for a decade at 300 kilograms of uranium -- not enough to convert to a stockpile of weapons-grade material.

"What is a more relevant fear would be that in Year 13, 14, 15, they have advanced centrifuges that enrich uranium fairly rapidly, and at that point, the breakout times would have shrunk almost down to zero," Obama said. 

The stark admission -- after his energy secretary even claimed the deal was a "forever agreement" -- came as the president seeks to quiet a growing chorus questioning whether the deal he and world leaders have negotiated merely delays the certainty of a nuclear-armed Iran. Obama has insisted confidently that Iran will not get a nuclear weapon on his watch, which ends in roughly 20 months, but has made no similar assurances about his successors. 

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Under the terms of the deal framework, Iran's breakout time would be expanded from the present two to three months to at least a year. But that constraint would stay in place only for 10 years, at which point some restrictions would start phasing out.

Although Obama acknowledged that Iran's breakout time could shrink, he said at least the world would have better insight into Iran's capabilities because of extensive inspections in the earlier years.

"The option of a future president to take action if in fact they try to obtain a nuclear weapon is undiminished," Obama said. 

Tehran has always maintained it doesn't want a nuclear bomb, but the international community has been skeptical, and America's close ally Israel considers a nuclear Iran an existential threat. U.S. lawmakers and foreign policy hawks have questioned how Obama can strike a diplomatic deal with a country that continues to threaten Israel and tops the U.S. list of state sponsors of terror.

Obama, who is also working to restore ties to longtime U.S. foe Cuba, has suggested cautiously in the past that a nuclear agreement could be a precursor to Iran pursuing a more amicable relationship with the world community. But in the days since the framework deal was announced in Switzerland, his administration has sought to emphasize that the deal relies on inspections, not trust, and is worthwhile even if the Iranian regime remains venomously anti-American.

"I think there are hard-liners inside of Iran that think it is the right thing to do to oppose us, to seek to destroy Israel, to cause havoc in places like Syria or Yemen or Lebanon," Obama said. "If they don't change at all, we're still better off having the deal."

In a portion of the same interview that aired Monday, Obama also rejected a call by Israeli Prime Minister Benjamin Netanyahu for any Iran nuclear deal to recognize his nation’s “right to exist,” claiming it would be a “fundamental misjudgment” to link the two issues.

“The notion that we would condition Iran not getting nuclear weapons in a verifiable deal on Iran recognizing Israel is really akin to saying that we won't sign a deal unless the nature of the Iranian regime completely transforms. And that is, I think, a fundamental misjudgment,” Obama said.

The comments were a rebuke to Netanyahu, who on Friday blasted the Iran framework deal and said his Cabinet is uniformly opposed to it. He also demanded that any final agreement include "a clear and unambiguous Iranian recognition of Israel's right to exist … the survival of Israel is non-negotiable." 

Obama also told NPR, “I want to return to this point: we want Iran not to have nuclear weapons precisely because we can't bank on the nature of the regime changing. That's exactly why we don't want to have nuclear weapons. If suddenly Iran transformed itself to Germany or Sweden or France, then there would be a different set of conversations about their nuclear infrastructure.”

The Associated Press contributed to this report.