The Italian government should keep the thousands of lives that were saved in mind when considering the future of the Mare Nostrum search and rescue operation, according to UNHCR's Italy protection officer Ricardo Clerici.
Addressing a conference to mark World Refugee Day, Mr Clerici declined to speculate on the future of the programme, but said it had been a "great humanitarian success".
Mare Nostrum, the EU's largest search and rescue operation, began last October after 366 migrants fleeing African countries drowned when their boat capsized a mile from Sicily.
After the tragedy, the EU pledged some €30 million in emergency funding, mainly targeted to fund immigration facilities on land.
The programme, however, is not expected to run forever and the Italian government has already described the operations as "unsustainable".
Mr Clerici said Mare Nostrum was estimated to have saved the lives of at least 5,000 migrants that would have died in sea crossings this year.
However, the number of boat migrants who have reached Italy this year has already topped the total of more than 40,000 for the whole of 2013. This, together with the high cost of running the programme, has seen increased pressure for the Italian government to cease the rescue missions.
Meanwhile, the Mare Nostrum operation has resulted in Malta receiving practically no migrants for months on end.
Organised by the UNHCR office in Malta, the conference also heard the first hand accounts of two migrants who had dared the perilous clandestine voyage to Malta.
Hannah Abraham Beraki, an Eritrean, said she crossed the desert in a pick up truck crowded with more than 30 people before being forced to hide behind a burka to do grocery shopping in Tripoli and eventually pay smugglers to bring her to Malta.
Mohamed Hussein Mohamed, a Somali, thanked the Armed Forces of Malta for saving his life.
He had spent six days at sea with some 40 people crowded in a small, engine-less dingy.