At least twice in the past month, a Russian delegation visited an airfield in Iran to examine weapons-capable drones, according to US national security adviser Jake Sullivan and satellite imagery obtained exclusively by CNN.

At Kashan airfield, situated in central Iran, Russian officials inspected Iranian-made Shahed-191 and Shahed-129 unmanned aerial vehicles (UAVs), commonly known as drones, CNN reported Friday (July 15).

Shahed-129, the first model of the series, was unveiled in 2012, with the Islamic Revolutionary Guard Corps (IRGC) claiming at the time that it was equipped with a 1,700km-range missile, capable of carrying eight air-to-surface missiles.

Both models are capable of carrying precision-guided missiles.

During a July 11 White House briefing, Sullivan said information received by the United States supported views that the Russian military is facing challenges sustaining its weaponry after significant losses in Ukraine.

Iran -- which has sought to establish itself as the hub of regional drone operations -- is planning to supply hundreds of drones with combat weapon capabilities to Russia for use in Ukraine "on an expedited timeline", he said.

"Our information further indicates that Iran is preparing to train Russian forces to use these UAVs, with initial training sessions slated to begin as soon as early July," he added.

At a White House briefing last Saturday, a senior administration official confirmed a statement Sullivan had made to CNN, saying, "We assess an official Russian delegation recently received a showcase of Iranian attack-capable UAVs."

The administration released satellite imagery demonstrating this, "as it suggests ongoing Russian interest in acquiring Iranian attack-capable UAVs", the senior official said, noting that the UAVs are clearly intended for use in Ukraine.

"To our knowledge, this is the first time the Russian delegation has visited this airfield for such a showcase," he said. "And we think it's of interest -- I mean, to put it mildly -- to what's happening here in the Middle East."

"Russia is effectively making a bet on Iran, and we are making a bet on a more integrated, more stable, more peaceful and prosperous Middle East region," the senior official said.

During the first Jeddah Security and Development Summit, held on Saturday, US President Joe Biden affirmed the United States' commitment to accelerate work with allies and partners in the Middle East to integrate and enhance security co-operation.

'Ability to build nuclear bomb'

Separately, the head of an advisory board linked to Iran's leadership said Iran has the technical capacity to build a nuclear weapon but has not taken a decision to do so, Al-Jazeera reported on Sunday.

The comments from former foreign minister Kamal Kharrazi came as talks to revive the 2015 nuclear deal have stalled and as the Iranian regime continues to push ahead with secret nuclear activities and other violations of the agreement.

A return to the deal, known as the Joint Comprehensive Plan of Action (JCPOA), would lift economic sanctions imposed on Iran, in exchange for its full compliance with the limits placed on its nuclear activities.

Yet Iran has continued to violate the terms of the agreement by expanding its nuclear activities and has circumvented sanctions repeatedly by engaging in illegal financial activities, according to recent findings.

The United States last Thursday vowed to "use all elements of its national power" to prevent Iran from ever acquiring nuclear weapons.

Asked how long the United States was prepared to give efforts to revive the 2015 nuclear deal, Biden said, "We're not going to wait forever."

Earlier this month, the International Atomic Energy Agency (IAEA) said Tehran had started "feeding... a cascade of... centrifuges" at a fuel enrichment plant.

The techniques facilitate the process and would make it easier for Iran to switch to a different level of enriching uranium.