US Secretary of Defence Lloyd Austin expressed alarm on Thursday over two Iranian ships that have entered the Atlantic and may be bound for Venezuela for a weapons delivery.
“I am absolutely concerned about the proliferation of weapons -any type of weapons – in our neighbourhood,” Mr Austin said during a Senate hearing.
Pressed by senators on the type of weapons the ships may be transporting, Mr Austin said he could not comment in a public setting, adding he had not had any discussions with any other nations in the western hemisphere - including Venezuela - on the issue.
Commercial satellite imagery from Maxar Technologies in April showed one of the ships carrying seven Iranian fast-attack boats similar to those used by the Iranian navy to harass US and other international vessels in the Arabian Gulf.
On Thursday, Iran state TV showed footage of the ships - the destroyer Sahand and the smaller vessel Makran – crossing into the Atlantic Ocean, a rarity for the Iranian Navy.
Richard Blumenthal, a Democratic senator from Connecticut, said the shipment “would fulfil a deal that Iran and Venezuela made a year ago” before President Joe Biden took office.
He stated that “allowing this ship to dock” causes Washington “grave concern".
The final destination and route of the ships remains unclear to US officials monitoring the situation.
Politico reported this week that the Biden team is privately urging Venezuela and Cuba to turn the ships away.
Pentagon spokesman John Kirby last week said the US reserves the right to take "appropriate measures” if the vessels pose a threat.
“The delivery of such weapons would be a provocative act and a threat to our partners in this hemisphere," Mr Kirby said.
"As such, we would reserve the right to take appropriate measures, in concert with our partners, to deter the delivery or transit of such weapons.
“This is a situation that the current administration inherited. We are now working to forestall [it] through diplomacy and other means,” he said.
Michael Singh, a senior fellow at the Washington Institute for Near East Policy, said that Iranian naval vessels crossing the Atlantic Ocean “is in itself not very concerning, much less threatening” but the transfer of weapons is.
"What's concerning is the possible transfer by Iran of fast-attack boats to Venezuela. Iran's naval forces have used these vessels to harass the US Navy and commercial shipping in the Gulf, and we would not want to see Tehran equip and train Caracas to replicate these tactics in the Caribbean," Mr Singh told The National.
Asked about US options, Mr Singh said that “certainly, the US can threaten Venezuela and Cuba with sanctions for allowing Iranian military ships to dock in their ports. The bolder option would be to interdict the shipment at sea, but that would depend on having the legal authority to do so".
Both Iran and Venezuela are subject to US sanctions and the delivery of fast-attack boats would be considered a breach of those measures.
If they are indeed headed for Venezuela, the ships are expected to dock there in about a month.
Last August, the US government seized four vessels carrying Iranian oil on their way to Venezuela,
The vessels were estimated to be carrying more than one million barrels of petroleum.
Relations between Iran and Venezuela have strengthened as they both continue to attempt to circumvent US sanctions.