The disappointment followed another letdown earlier in the day, when the navy said satellite calls detected over the weekend did not in fact come from the vessel.
The search and rescue operation is being led by Defense Minister Oscar Aguad. When the sub last made contact on Wednesday, five days ago, it was immersed, Balbi said.
Gonzalez said the navy had intensified an aerial hunt off the country's southern Atlantic coast after adverse weather conditions spurred waves up to 26 feet (8 metres) and made a maritime search hard. The oxygen situation could be helped, even if the vessel bobs adrift on the surface with the hatch open. Although the submarine has enough food and fuel to last for 90 days and enough oxygen for 30 days on the surface, it only had enough oxygen to survive for seven days if submerged.
In addition to the UUVs, the USA has deployed aircraft to assist in the search, as well as underwater equipment specifically designed for submarine search and rescue. "This is why we are deploying all resources with high tech sensors. We welcome the help we have received to find them". A man walks past a banner in the colours of the Argentine national flag, outside the Argentine Naval Base where the ARA San Juan submarine that is missing at sea sailed from, in Mar del Plata, Argentina November 20, 2017. The vessel had been due to arrive at its destination Sunday.
"A warship has a lot of backup systems, to allow it to move from one to another when there is a breakdown", naval commander Gabriel Galeazzi said.
The sub was journeying from the extreme southern port of Ushuaia to the coastal city of Mar del Plata.
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This type of problem is considered routine, and the crew was reported safe, he added.
The Argentine navy had one more communication with the captain before the sub went missing, said Galeazzi. The Argentine navy said an electrical outage on the diesel-electric-propelled vessel might have downed its communications.
The ARA San Juan was inaugurated in 1983, making it the newest of the three submarines in the navy's fleet.
The ARA San Juan is a TR-1700 submarine manufactured in Germany, commissioned by the Argentine Navy in 1985.
If the hull is intact, it can withstand ocean depths up to about 600 meters, Layton said.
Earlier hopes that searchers may have heard communication attempts by the crew have not panned out, the military said. But later analysis determined the noises were not from the missing vessel, but instead might have been from the ocean or marine life, Balbi said. But officials later said those calls had not come from the missing sub.