The Royal Navy has deployed an ice patrol ship to help search for an Argentinian submarine that is missing with 44 people on board.
Contact with the Argentine military sub ARA San Juan was lost three days ago.
Ships and aircraft have been scrambled to search for the vessel in the southern Argentine Sea, but the search efforts have been disrupted by a storm.
Powerful winds and waves up to six metres (20ft) high have made exploration exceptionally difficult, according to Argentine navy spokesman Enrique Balbi.
The Argentine navy anticipates the poor conditions to continue through to Sunday afternoon, according to a Reuters report.
A spokesman for the British Navy said: "Following a request from the Argentine government, HMS Protector has been deployed to join the search and rescue effort for the ARA San Juan."
An offer of help from an explorer aircraft belonging to the United States has also been accepted by Argentina.
Sky News' Defence Correspondent Alistair Bunkall said Britain also has an C-130 Hercules, which is stationed in the Falklands Islands, on standby if required.
The ARA San Juan last gave its location two days ago and Mr Balbi has explained that the weather is complicating efforts, which are taking place both above and below the surface
"Detection has been difficult despite the quantity of boats and aircraft" involved in the search, Mr Balbi said.
He said the vessel may be suffering from a communications error.
"We are investigating the reasons for the lack of communication. If there was a communication problem, the boat would have to come to the surface," he added.
Mr Balbi said the submarine, which left the southern city of Ushuaia for Mar del Plata, more than 1,800 miles away, has food supply for several days and is likely to continue its journey despite the problem.
According to national Argentinian newspaper La Nacion, the 66m (216ft) long, diesel-electric vessel was subjected to complex repair and engineering work in 2008, which the country's navy believed would extend its life by 30 years.
It was built in Germany in 1985 and arrived in Argentina a year later.
Argentina's President Mauricio Macri said the government was in contact with the crew's families.
"We share their concern and that of all Argentines," he wrote on Twitter.
"We are committed to using all national and international resources necessary to find the ARA San Juan submarine as soon as possible."
Pope Francis, who is from Argentina, has also offered his "fervent prayers" for the 44 crew members via a telegram to a senior bishop in the country.
The Pope expressed his spiritual closeness to the families of the sailors, as well as the military and civil authorities in Argentina.