* At least 25 migrants die during weekend Mediterranean crossings
* Italy says has rescued almost 4,000 in last 48 hours
* Italy threatens to halt sea search and rescue mission
* Italian minister to meet EU commissioner Wednesday
By Gavin Jones
ROME, Aug 25 (Reuters) - Italy's search and rescue services have found six more bodies in the Mediterranean to add to the death toll of 19 over the weekend, the navy said on Monday, with no let-up in the record numbers risking the perilous crossing to Europe from Africa.
The navy said it had rescued almost 4,000 migrants over the weekend and Italian vessels were continuing to look for victims of a boat which capsized north of the Libyan coast on Sunday evening.
The names and nationalities of the casualties were not released.
Record high number of migrants by sea to Italy this year are putting enormous pressure on the Italian coast guard and navy. At the weekend Italy urged the European Union to take over sea patrols in the Mediterranean and hinted it could stop sending its ships out to search for boats in distress if the EU didn't take responsibility.
Calmer summer seas have led more people to make the crossing from North Africa, where a breakdown of order in Libya has been exploited by human traffickers, pushing the number of arrivals into Italy since January past 100,000.
Interior Minister Angelino Alfano on Sunday stepped up calls for the European Union to take over responsibility for Italy's "Mare Nostrum" (Our Sea) patrols, which have rescued tens of thousands of migrants from boats in distress.
The search and rescue mission, which began after a shipwreck near Italy's coast killed 366 people last October, has sparked fierce debate in Italy, which feels isolated by the EU.
"Only the blind can't see what is happening: the more the situation on the Mediterranean border worsens, the clearer it becomes that Mare Nostrum has to be substituted by joint European action," Alfano said.
In a threat to end the mission, he said if the EU fails to take over from Italy, the government will "take our own decisions and take responsibility for them, because we can't go on like this."
European Home Affairs Commissioner Cecilia Malmstrom on Sunday thanked Italy for its efforts in assisting migrants and said she would be meeting Alfano in Brussels on Wednesday.
Prime Minister Matteo Renzi has called on the European Union to address the migrant crisis by investing in border control agency Frontex, and on the United Nations to intervene in Libya to manage the flows of refugees.
At the frontier between Europe and Africa, Italy has long attracted seaborne migrants, but arrivals this year are already far above a previous record of just over 60,000 for all of 2011, when the Arab Spring uprisings fuelled migration.
Around 1,370 migrants rescued in the last 24 hours, including 192 women and 156 children are due to arrive in the southern Italian mainland port of Crotone later on Monday, the navy said. (Editing by Susan Fenton)