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A U.S. naval ship is pictured during the Velayat-90 war game in the Sea of Oman, near the Strait of Hormuz in southern Iran December 29, 2011. A senior Iranian Revolutionary Guards commander said on Thursday that the U.S. was not in a position to tell Tehran "what to do in the Strait of Hormuz", state television reported. Reuters/Abdollah Arab Koohsar/Fars News

US defence officials said that the 10 American sailors who were detained in Iran since Tuesday are expected to be released soon. The US received high level assurances from Tehran that the crew would be returned to the US navy in international waters early on Wednesday.

A senior US official told the CNN that there has been a voice contact with the sailors detained in the US and that they are expected to be released during the daylight hours on Wednesday.

"Certainly, everybody should be aware of the fact we have been in touch with the Iranians and they have assured us that our sailors are safe and that they'll be allowed to continue their journey promptly," White House Press Secretary Josh Earnest said. He added that US President Barack Obama will be in touch with the Congress members regarding the incident.

The US is uncertain whether the two US navy boats entered the Iranian waters intentionally. A senior defence official said that no distress call was made by the crew of the ships. According to another senior defence official, the US navy boats were sailing near the Farsi Island looking to refuel; however, it is not clear whether they had refuelled.

The two vessels lost contact with the US while they were transiting the Gulf from Kuwait to Bahrain. They eventually ended up in the custody of Iran. US Secretary of State John Kerry immediately contacted Iranian Foreign Minister Mohammad Javad Zarif after he learnt of the incident. Kerry explained to Zarif that the boats strayed because of some mechanical problems, to which Zarif assured that the sailors will be released soon.

The 10 Americans, including a woman, were taken into custody by the country’s powerful Revolutionary Guards’ naval force, Iran’s semi-official Fars news agency reported. According to Fars, the two boats were near the Farsi Island, which is the Revolutionary Guards base, when they were intercepted.