MANAMA, Bahrain >> A year after he struck the outlines of a nuclear deal with Iran, Secretary of State John Kerry finds himself confronting a new challenge from Tehran: While it is observing the nuclear agreement to the letter, its missile launches, arms shipments to Yemen and involvement in Syria have, if anything, accelerated.

Kerry arrived here for a meeting of the Arab states this week with the objective of reassuring them with an array of plans for new missile and cyberdefenses. Instead, he found himself disputing the argument of one leading diplomat from the United Arab Emirates that Tehran today is “as dangerous as ever.”

Without nuclear fuel or the ability to produce more, Kerry argued, Iran is far less of a threat than it was, adding that “the crisis was the potential of a nuclear weapon.”

But his hosts at a meeting of the Gulf Cooperation Council echoed the concern here on Thursday that, even with the nuclear threat off the table, the Islamic Revolutionary Guard Corps seemed to be active everywhere.

“We are noticing two things that we kind of have expected,” Bahrain’s foreign minister, Sheikh Khalid bin Ahmed al-Khalifa, said at a joint news conference with Kerry. “The missile program is moving forward with full support from the top of the leadership of the Islamic Republic, and we are seeing the hegemonic interventions” by Tehran “continuing unabated.”

Kerry is fully acknowledging those facts. On Thursday morning, touring the sprawling naval base of the U.S. 5th Fleet here, he was briefed on four interceptions in recent months of Iranian shipments of small arms headed to Yemen.

“No one made a pretense that other challenges we knew existed were suddenly going to be wiped away,” he said about the aftermath of the nuclear agreement. But there was a hope that over the long term Iran would change its fundamental behavior in the Middle East — an underlying bet behind the administration’s decision to seek the nuclear accord — and a year later Kerry is conceding that at best an argument rages inside Iran about changing course.

“Clearly, there is a difference of opinion within Iran itself,” he said.

Hours before leaving New York on Tuesday, Kerry noted that Iran’s supreme leader, Ayatollah Ali Khamenei, recently denounced a former president, Hashemi Rafsanjani, who had argued for engaging in more dialogue and less missile manufacturing.

“He was rebuked publicly by the supreme leader, who said, ‘No, it’s missiles, not dialogue,’” Kerry said on MSNBC’s “Morning Joe,” shaking his head.

That reality has forced Kerry to make a complex argument here to the ministers of the Gulf Cooperation Council, before a visit by President Barack Obama to Saudi Arabia this month.

Kerry repeated Thursday that the United States would continue to lift the economic sanctions against Iran that it agreed to as part of the nuclear accord, even while imposing new ones to counter Tehran’s missile launches, an effort underway in the U.N. Security Council.

Diplomats say it is doubtful the United States will win that argument in the Security Council. Russia has noted that while the missile launches may violate the spirit of Resolution 2231, passed after the Iran deal, they are still allowed within the strict meaning of its words.

Indeed, the older resolution, which Tehran also routinely ignored, stated that “Iran shall not undertake any activity related to ballistic missiles.” But the new resolution — the wording of which was negotiated in Vienna in July, just as the final nuclear accord was taking place — is significantly weaker. It “calls upon Iran not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons.”

The Iranians argue that the language is nonbinding. And increasingly they are making the case that they are not seeing the benefits of sanctions relief: While their oil sales are up, they have not gained the access to global financial markets that had been held out as a reward for completing the deal.

But lurking beneath the details of missile launches is a more fundamental set of frustrations between Washington and its Arab neighbors, edging into distrust. The Saudis appeared somewhat shocked to read, in Jeffrey Goldberg’s series of interviews in The Atlantic, that Obama referred to them as “free riders’; while it was hardly a new sentiment, even Kerry’s staff members winced to read it coming from the president.

Obama went on to say that the Saudis, and by extension their smaller Sunni Arab neighbors, needed to “find an effective way to share the neighborhood and institute some sort of cold peace.” He rejected the idea that the United States would constantly side with the Arab states, noting that “would mean that we have to start coming in and using our military power to settle scores — and that would be in the interest neither of the United States nor of the Middle East.”

Donald Trump, the Republican front-runner in the presidential race, has gone considerably further, arguing in an interview with The New York Times that he would boycott Saudi oil if the country did not contribute more to fighting the Islamic State. Arab diplomats gathered here said they understood the difference between campaign talk and policy, but added that Trump’s remarks still made them queasy about the future of the security relationship.

Nonetheless, evidence that the Arab states represented here are rushing to deal with their own defensive shortcomings is scarce. In a background briefing for reporters before Kerry’s trip, a senior State Department official, who was granted anonymity under the rules of the briefing, acknowledged that for all the talk of building a regional missile defense system, there is still no agreed-upon “architecture,” meaning where radars and missile batteries would be placed.

Similarly, while there are bilateral discussions about cyberdefenses, there is no overall strategy about deterring Iranian cyberattacks. In testimony this week to the Senate Armed Services Committee, Adm. Michael S. Rogers, head of U.S. Cyber Command, noted that Iranian cyberattacks on the United States had diminished since the nuclear deal was signed, but suggested that regular attacks by Iran continued in the region.

Kerry has been measured in his critiques of Iran, noting Thursday that it had “helped on a few things,” including getting an agreement for a cessation of hostilities in Syria. But he cited the interceptions by British, French and American ships of arms headed to Yemen, and said “it is not constructive to be sending dhows across the Gulf loaded with weapons that are only going to add fuel to the fire of a war we are busy trying to end.”

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