The crew of the Cheeki Rafiki, a 40-foot performance racer/cruiser, first ran into difficulties on Thursday some 1,000 kilometres east of Cape Cod in Massachusetts.
The yachtsmen were returning from Antigua Sailing Week in the Caribbean.
They were diverting to the Azores, the Portuguese island group, on Friday when contact with the yacht was lost.
The men were sailing the boat back to Southampton on the southern English coast for the yacht training and charter company Stormforce Coaching.
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"Unfortunately we lost contact during the early hours of Friday morning and we believe it is possible the crew abandoned to the life raft.
"Search and Rescue authorities were mobilised and a mixture of Canadian and US aircraft along with merchant vessels searched throughout Friday and yesterday.
"Although the search efforts co-ordinated by Boston were exceptional we are devastated that the search has now been called off so soon.
"Our thoughts are with the four yachtsmen and their families and we hope and pray for them all."
"We are in continual contact with the US coastguard and are providing consular assistance to the families.