CAMP DAVID, Maryland – US President Barack Obama hosted leadership from the Gulf Cooperation Council (GCC) on Thursday at his retreat in Camp David, hoping to sell skeptical Arab powers on the strength and durability of a deal with Iran over its nuclear program.The regional council seeks written assurances after two years of US-led negotiations with Iran produced a framework agreement last month, allowing much of its nuclear infrastructure to remain in place.Arab leaders have reportedly threatened to match whatever nuclear capability Tehran is allowed to retain under a future comprehensive accord.But the White House denied those claims on Thursday afternoon, stating that no such proposal had come up in weeks of consultations leading up to the summit.Speaking with reporters on the sidelines of the summit, deputy national security adviser for strategic communication Ben Rhodes told reporters that GCC nations were more concerned about Iran’s “destabilizing” activities in the region than they are with the contents of the nuclear deal. The GCC leadership has expressed appreciation for the “unprecedented transparency” codified in the deal, he said.The White House sent out invitations to Gulf leaders shortly after the framework was announced in Lausanne, Switzerland, on April 2. The focus of the summit, White House officials say, is to bolster and synthesize GCC defense structures in order to counter aggressive Iranian behavior.Iran’s asymmetric strategies in Lebanon, Syria and Yemen are “very low costs,” Rhodes argued, countering concerns that sanctions relief for Iran will bolster its regional activity. Tehran’s aggression was underscored on Thursday – just hours before the meeting began at the buttoned- down retreat – when Iranian ships opened fire on a Singapore-flagged ship crossing through international waters in the Gulf.The Alpine Eternity, a 29,130 gross tons oil products tanker, safely reached the United Arab Emirates port of Jebel Ali after coming under attack in the Gulf, its manager said.The White House said that while details of the incident were still unknown, the action was “exactly” what concerns the US and its Gulf partners about Iran’s foreign policy. The Obama administration argues these moments underscore the need for a nuclear deal, since a nuclear-armed Iran will only prove more assertive, and that such a scenario is the most likely alternative to a deal.But Arab powers fear the deal is the opening salvo of a larger rapprochement between the US and Iran, and the beginning of a realignment away from the Gulf council.Rhodes pushed back against this notion, arguing that a nuclear deal will be merely transactional. The purpose of the summit is to underscore that policy with defense commitments, he said.Obama flew to Camp David Thursday morning on Marine One, accompanied by Rhodes, national security adviser Susan Rice and press secretary Josh Earnest.Much of the president’s national security council is present for the summit, including Secretary of State John Kerry, Secretary of Defense Ashton Carter, CIA director John Brennan, Homeland Security Adviser Lisa Monaco and Secretary of Energy Ernest Moniz, considered the administration’s “science man” on the framework deal with Iran.Representing the GCC is Saudi Arabia’s interior minister, Crown Prince Muhammad bin Nayef, and its defense minister, Deputy Crown Prince Muhammad bin Salman; as well as the United Arab Emirates’ Crown Prince Sheikh Muhammad bin Zayed al-Nahyan, Oman’s Deputy Prime Minister Sayyid Fahd bin Mahmoud Al Said and Bahrain’s Crown Prince Salman bin Hamad bin Isa al-Khalifa. Two heads of state, the emirs of Qatar and Kuwait, are present for the rare meeting.The summit was broken into three working sessions over six hours at the presidential retreat, where Obama last received foreign leaders during the G8 Summit in 2012.The first session was devoted to discussion on Iran, and the parties are expected to discuss threats emanating from Syria, Libya and Yemen over the course of the day.Israel was not mentioned as a major point of discussion at the summit.The GCC seeks advanced weapons systems and contract offers, while the US seeks agreement on a broad structural defense design that would efficiently coordinate Gulf maritime, counterterrorism, air and antimissile systems.The Obama administration has long advocated for a missile defense system across the region, his aides point out. The summit is intended to expand the scope of US security guarantees to its Arab allies beyond that single portfolio.