US President Barack Obama on Wednesday said Israel was the only country to object to the Iran nuclear deal, opposition he said was “sincere” but “wrong.”

In an address to the American University in Washington, Obama said the Iran deal was “the strongest nonproliferation agreement ever negotiated. And because it’s such a strong deal, every nation in the world that has commented publicly, with the exception of the Israeli government, has expressed support.”

The UN Security Council has “unanimously supported it,” Obama added, as well as over “100 former ambassadors who served under Democratic and Republican presidents.”

“I’ve had to make a lot of tough calls as president. But whether or not this deal is good for American security, this isn’t a hard one, it isn’t even close,” he said.

Netanyahu ‘sincere,’ but ‘wrong’

Obama said he believes Prime Minister Benjamin Netanyahu is “sincere” in his opposition, but “wrong.”

“When the Israeli government is opposed to something, people in the United States take notice. They should,” Obama said. Iranian leaders “deny the Holocaust,” and “facilitate the flow of rockets” on Israeli cities. “In such a dangerous neighborhood, Israel has to be vigilant.” Obama said.

Israel “rightly” says it can only rely on itself for its security, he added.

Nonetheless, the president argued that thwarting Iran’s nuclear program, something he said the deal successfully does, remains the top priority.

“A nuclear-armed Iran is far more dangerous to Israel, to America, and to the world, than an Iran that benefits from sanctions relief. I recognize that Prime Minister Netanyahu disagrees. I don’t doubt his sincerity. But I believe he is wrong,” Obama said.

Lashing out at unnamed critics of the deal, Obama said those who opposed the interim deal “were wrong,” and were now using the success of the interim deal to buttress its opposition to the nuclear deal.

“When the interim deal was announced, the critics, the same critics we’re hearing from now called it a historic mistake… The critics were wrong,” Obama said. “The progress of Iran’s nuclear program was halted, for the first time in a decade…. Inspections did increase. There was no flood of money into Iran. And the architecture of the international sanctions remained in place.”

The critics are right in one respect, he said. “Walk away from this and you will get a better deal,” Obama said, “for Iran.”

As “president of the United States, it would be an abrogation of my constitutional duty” to fail to pursue a policy good for America “simply because it causes friction with a friend and ally,” Obama said.

‘Diplomacy or war’

The only alternative to the deal is war, Obama maintained, adding that he is not saying this to “be provocative.”

It’s “diplomacy or some form of war. Maybe not tomorrow. Maybe not three months from now, but soon,” Obama said.

The president said he has not hesitated to use force during his term.

“There are times when force is necessary, ” the president said. If Iran does not abide by the deal “it’s possible war” will become necessary, he conceded. “But how can we justify” military action before trying a diplomatic approach? he asked.

The military option would not be as effective as diplomacy, Obama stressed, noting that Israeli analysts have said a strike would only set back Iran’s nuclear program by a few years.

He said that under the deal, it would be difficult for Iran to cheat, arguing that it would have to build “a secret source for every aspect of its program,” something the president said no other nation had succeeded in doing with such stringent oversight.

Obama said the US had “no illusions” about Iran’s support for terror groups such as Hezbollah. “But they engaged in these activities for decades. Before sanctions, and while sanctions were in place. They even engaged in them during the Iran-Iraq War, which cost them a million lives. The truth is Iran has always found a way to fund these efforts.”

Moreover, Israel and the Gulf states have larger defense budgets, Obama said.

“Iran’s defense budget is eight times smaller than the combined Gulf allies. Its military will never compare to Israel’s, and our commitment to Israel’s qualitative military edge will guarantee that,” Obama said.

Obama said those who were pushing for a better deal either didn’t understand the Iranian public or were purposely misleading the US public.

“Just because hardliners chant ‘death to America’ doesn’t mean that’s what all Iranians believe. Those hardliners have been opposed to the deal. They’re making common cause with the Republican caucus,” said Obama. “The majority of the Iranian people have powerful incentives to urge their government to move in another direction. We should offer them that chance, that opportunity.”

Obama said that the opposition to the deal was emerging from those who supported the Iraq war in 2003, a conflict he said bred the Islamic State, and “ironically” improved Iran’s regional standing.

The speech, which was supposed to start at 11:20 a.m., was delayed by over 25 minutes. No reason was given for the delay.