The US was monitoring Iranian ship movements in the Middle East as Tehran quietly replaced a spy ship, Saviz, in the Red Sea damaged in an April attack, two US officials told CNN.
Tehran towed the vessel back to port and brought a similar one to gather intelligence in the waterway amid escalating regional tensions and an ongoing maritime shadow conflict between Israel and Iran.
The Iranian ship registered as a general cargo vessel, Behshad, left the port of Bandar Abbas in early July, reaching its destination nine days later, according to satellite imagery provided to CNN in a report from ImageSat International, an Israeli satellite and intelligence company, which tracked the ship's journey.
Behshad stopped near the Bab el-Mandeb strait, a crucial waterway that controls access to the Red Sea and the Suez Canal.
A few days later, Saviz, another Iranian ship registered as a cargo vessel that had been patrolling those waters for five years, began its journey back to Iran, accompanied by two tugs.
The ships are currently south of Oman, based on satellite images from ImageSat.
The two officials explained that Saviz was listed as a cargo ship and used by Iran's Revolutionary Guard Corps (IRGC) to gather intelligence in the critical waterway and assist Iran's Houthi allies in Yemen.
Former President Donald Trump sanctioned both the Saviz and the Behshad in 2018 as part of his maximum pressure campaign on Iran.
In an early April attack, the ship sustained damage when an Israeli commando attached an explosive to its side.
Iran admitted the attack, and its media published pictures of flames and smoke rising from the wrecked ship in the Red Sea.
A US official announced that Tel Aviv informed Washington of the attack, which they described as a retaliation for the previous Iranian strikes on Israeli ships, pointing out that Saviz was damaged underwater.
The US Naval Institute published a report in October 2020 that asserted the Saviz was a covert military ship operated by the IRGC.
The report said that uniformed men were present on board and that a boat type used by the Revolutionary Guards, with a hull similar to a Boston Whaler, was on the ship's deck.
The attack with the limpet mine, which is an explosive attached to the side of a ship, often just below the waterline, came as international negotiators were making progress on a return to the Iranian nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), which Israel openly opposes.
The maritime shadow conflict between Iran and Israel reached new heights last week with the drone attack on Mercer Street, a Liberian-flagged tanker with ties to an Israeli shipping billionaire.
A Romanian and a Briton were killed in the attack off the coast of Oman, which the US, UK, and others have blamed on Iran.
Iran has denied any involvement in the attack but the US has called for a coordinated response against Tehran.
Tensions also escalated last Wednesday when Iranian gunmen seized the Asphalt Princess ship off the coast of the United Arab Emirates for several hours.
On Thursday, Israeli Defense Minister Benny Gantz responded "yes" when asked by a media outlet whether Israel was ready to attack Iran. However, Gantz and other Israeli officials have stressed the need for a united diplomatic front against Tehran.
Saeed Khatibzadeh, the spokesman for Iran's foreign ministry, wrote on Twitter on Thursday that any Israeli military action against the country would be met with a "decisive" response.
Khatibzadeh called the Israeli threat of military action a "brazen violation of international law" and warned, "don't test us."
