The U.S. Navy said Saturday it is joining the search for an Argentine navy submarine with a 44-person crew that has been out of radio contact for several days.

U.S. Southern Command has directed the Navy to deploy a P-8A Poseidon to help in the search for the submarine, which was on a routine mission when it went missing. The ARA San Juan was last heard from Wednesday morning.

The U.S. Navy aircraft will join a growing international effort to try and find the submarine, which was sailing from Tierra del Fuego on the southern tip of South America to its base at Mar del Plata, south of Buenos Aires.

The P-8A and its 21-person crew will depart El Salvador's Comalapa Air Base, where it was supporting counter-narcotics smuggling operations, the Navy said.

"The P-8A Poseidon is the Navy's newest maritime, patrol and reconnaissance aircraft and is configured with state-of-the-art sensors and communications equipment, allowing it to support a wide range of missions over large bodies of water, including sub-surface search-and-rescue operations," the Navy statement said.

The ARA San Juan is a German-build, electric-diesel powered submarine. The Argentine navy said the crew would normally bring the ship to the surface if it lost radio communication with the mainland.

An Argentine destroyer and two corvettes are conducting a search around the area of the sub's last known position off the southeastern Valdez Peninsula, according to a BBC report. The search has been hampered by high winds and choppy conditions.

The rescue operation has been formally upgraded to a search-and-rescue, navy spokesman Enrique Balbi told a news conference, according to the BBC.

Adm. Gabriel Gonzalez, chief of the Mar del Plata base that was the submarine's destination, said the vessel had sufficient food and oxygen, according to the Associated Press.

A number of countries in the region have offered to participate in the search.