The ARA San Juan (pictured in a file photo) last contacted the Argentine navy on Wednesday while 250 miles off the coast of Patagonia and has not been heard from since

The ARA San Juan (pictured in a file photo) last contacted the Argentine navy on Wednesday while 250 miles off the coast of Patagonia and has not been heard from since
The US Navy has deployed one of its high-tech surveillance aircraft to help find a missing Argentine attack submarine which went missing three days ago.

NASA has also sent a surveillance aircraft to the scene, diverting it from a mission studying Antarctic ice.

The ARA San Juan was last in contact with its base on Wednesday when it was almost 270 miles from the coast of Patagonia.

The US Navy diverted one of its P-8A Poseidon maritime surveillance aircraft to Bahia Blanca, Argentina to help with the search for the missing submarine.

According to the US Southern Command: 'The aircraft and its 21-person crew will depart El Salvador's Comalapa Air Base, where it was supporting counter-illicit trafficking maritime patrol operations.

'Once in Bahia Blanca, they will join the ongoing international search for the Argentinean Navy vessel and its crew, as requested by the government of Argentina.'

The US Navy said the P-8A Poseidon is its newest patrol and reconnaissance aircraft with 'state-of-the-art sensors and communications equipment'.

It can spend four hours patrolling a search area and has a range of 1,200 miles.

Argentine naval spokesman Enrique Balbi said the emergency operation was formally upgraded to a search-and-rescue procedure on Friday evening after no visual or radar contact was made with the submarine.

Argentine naval officials hope the submarine may have suffered a communication problem and is currently on the surface although there have been no radar or visual sightings

Argentine naval officials hope the submarine may have suffered a communication problem and is currently on the surface although there have been no radar or visual sightings
He said: ' Detection has been difficult despite the quantity of boats and aircraft.'

High winds and heavy seas have hampered the search.

The navy believes the submarine, which left Ushuaia en route to the coastal city of Mar del Plata in Buenos Aires province, had communication difficulties that may have been caused by an electrical outage, Balbi said.

Navy protocol would call for the submarine to come to the surface once communication was lost.

He said: 'We expect that it is on the surface.'

The German-built submarine, which uses diesel-electric propulsion, was inaugurated in 1983, making it the newest of the three submarines in the navy's fleet, according to the navy.

President Mauricio Macri said the government was in contact with the crew's families.