Story highlights Only 30% of Americans see Iran as a serious threat, the lowest number in CNN polling back to 2000

63% say Trump has been more reckless than responsible on North Korean threats

Washington (CNN) Two in three Americans say President Donald Trump should not pull the United States out of the nuclear deal aiming to block Iran from developing nuclear weapons, according to a new CNN poll conducted by SSRS.

Trump announced his intent to decertify the agreement last week. But eight in 10 Democrats and two in three independents oppose withdrawing from the agreement. Even in the President's own party, Republicans are evenly split, with 48% wanting to remain and 47% to withdraw.

Concern about Iran has slipped among Americans since the deal was put in place. Only three in 10 adults say the threat is "very serious," down from nearly half, 49%, in September 2015. That marks the smallest share of those concerned in CNN polling dating back to 2000. Still, nearly seven in 10 adults overall, 69%, say Iran poses a serious threat to the US.

Republicans are more likely to view Iran as a very serious threat than Democrats, 45% versus 26%. But only half the gap that existed two years ago, when Republicans were 36 points more likely than Democrats to see Iran as a deeply serious threat.

After Trump announced his decision on the deal, Iran's supreme leader, Ayatollah Ali Khamenei, said in public comments on Wednesday that "it would be a waste of time to respond to such blatherings and nonsensical remarks by the foul-mouthed US President."

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