Italy summoned Austria's ambassador on Tuesday after Vienna threatened to send troops to the border over the migrant crisis, as the influx to Europe across the Mediterranean topped 100,000 for 2017.
Defence Minister Hans Peter Doskozil had on Monday said Austria would close its border with Italy and send soldiers to guard it if there was no slowdown in arrivals.
Announcing that arrivals had passed the 100,000 mark for 2017, the UN's International Organization for Migration (IOM) said nearly 2,250 people had died so far this year attempting to make the perilous crossing in rickety boats.
Italy has taken in nearly 85 percent of this year's arrivals -- most of them sub-Saharan Africans crossing from Libya -- and has pleaded for help from other European Union nations, saying it is struggling to cope.
"The reception of rescued migrants cannot be seen as an issue only for Italy, but a matter for Europe as a whole," IOM chief William Lacy Swing said, appealing for the rest of the EU to show more solidarity.
On Sunday, Italian Interior Minister Marco Minniti called on EU neighbours to open their ports to rescue ships picking up migrants, after issuing a drastic threat to close its own ports to the boats.
But France rejected that idea, with an aide to Minniti's counterpart Gerard Collomb telling AFP this would only encourage more migrants to set sail.
EU interior ministers are due to meet in Estonia's capital Tallinn on Thursday to discuss the migrant crisis -- the continent's worst since World War II -- in a bid to defuse a long-running row over spreading asylum seekers across the bloc.
The EU put in place a policy in 2015 to distribute around 160,000 asylum-seekers across different countries.
But only about 20,000 have been relocated from Italy and Greece under the scheme, while Hungary, Poland and the Czech Republic have flatly refused to take part.
Ministers meeting in Tallinn will also discuss a "code of conduct" for charities operating rescue boats in the Mediterranean, a plan announced by France, Germany and Italy on Monday.
Separately, foreign ministers from European and African countries affected by the crisis will meet in Rome on Thursday with representatives of the EU and UN as part of a diplomatic push to stem the influx.
In an interview with France's Figaro newspaper, European migration commissioner Dimitris Avramopoulos called on Tuesday for EU countries to speed up deportations of failed asylum seekers to ease the pressure, but warned this needed cooperation from their home countries.
The UN figures show that between January 1 and July 3, more than 85,000 migrants landed in Italy, nearly 9,300 in Greece, nearly 6,500 in Spain and over 270 in Cyprus.
"We are under enormous pressure," Italy's Minniti told newspaper Il Messaggero over the weekend, while the country's Red Cross warned that the situation in overcrowded reception centres was becoming critical.
The UN's refugee agency also weighed in, warning that Italy cannot continue absorbing tens of thousands of migrants on its own.
"This is not sustainable. We need to have other countries joining Italy and sharing that responsibility," said Vincent Cochetel, UNHCR special envoy for the central Mediterranean.
While the numbers arriving in 2017 are staggering, they remain far below last year's figures.
During the same period in 2016, 231,503 people made the crossing to Europe, with the 100,000-mark passed already in February that year.
But at that time most of the migrants were crossing from Turkey to Greece, and an EU deal with Ankara in March last year effectively hit the brakes on that movement.