Another point of friction is how the burden can be shared across the EU -- especially when large swathes of the population are increasingly hostile to the idea of taking more migrants.
German Chancellor Angela Merkel allowed more than one million asylum seekers into the country in 2015, a decision that was welcomed at the time but has fuelled anti-immigrant sentiment in Europe's biggest economy.
Merkel's CDU party suffered stinging losses in last year's general election, and she only just managed to hang on to power, while the far-right anti-immigrant, anti-Islam AfD party won seats in parliament for the first time.
The CDU's Bavarian sister party, the CSU, has since threatened to shutter German borders if Merkel does not adopt a harder position on migration, an impasse that could topple her government.
An opinion poll last week showed that nearly 90 percent of Germans favour a tougher stance on migration.
The main gateway into Europe for refugees arriving by sea, Italy is struggling under the burden placed on it by the so-called Dublin rules, which require migrants to apply for asylum in the first country they enter.
An anti-migrant coalition between Italy's far-right and anti-establishment parties was sworn in to government earlier this month after March's election.
One of its first decisions was to refuse to allow the Aquarius rescue ship carrying 630 migrants to dock in Italy.
Italy has seen around 700,000 migrants arrive since 2013. Since January 1, the number of new arrivals has fallen by 78 percent to just over 15,600, according to data compiled by the interior ministry.
France, one of the countries where many migrants have said they would most like to settle, has also experienced tensions, particularly at its border with Italy which authorities have attempted to close.
The majority of French people have said they are opposed to illegal immigration, with 56 percent saying they were against the Aquarius being allowed to dock in France.
Nearly half of the 630 migrants on board, mostly of African origin, want to apply for asylum in France.
Last year asylum applications in France rose to more than 100,000, a 17.5 percent increase.
Conservative Chancellor Sebastian Kurz, who claims to have helped shut down the so-called Balkan route for migrants in 2016, said Tuesday the debate in Germany could help accelerate efforts to find a Europe-wide solution.
Austria received 200,665 applications for asylum between 2013 and 2017, equivalent to 2.3 percent of its population of 8.7 million.
After peaking at 88,160 in 2015, the annual figure fell to 24,715 in 2017.
Belgium awarded refugee or equivalent status to around 40,000 people between 2015 and 2017, according to official data.
The government has toughened its stance, particularly under the state secretary for asylum and migration, Theo Francken, who recently said he was opposed to all illegal immigration in the EU and that only refugees who have been sent from UN-administered camps in war zones should be allowed in.
Hungary, Czech Republic, Poland, Slovakia
The four so-called Visegrad countries are opposed to any refugee quota system that the EU has tried to impose on them in the two years since the migrant influx peaked at more than 1.26 million in the entire bloc in 2015.
Spain is the third main point of arrival after Italy and Greece, but seems to be one of the few countries within the bloc where public opinion is not deeply divided. And more than 9,300 migrants have arrived on the Spanish coast since the beginning of the year, double the number for the same period in 2017.
The new Socialist government under Pedro Sanchez agreed to allow the Aquarius to dock and to handle the migrants' applications for asylum. He argued that the crisis over the boat should help "nudge" other countries within the bloc.
Sweden, which previously had a very open refugee policy, has toughened its stance since the end of 2015.
According to the official figures, it awarded asylum to more than 144,000 people, primarily from Syria, between 2015 and 2017, compared with an overall population of under 10 million.
Immigration is one of the main issues in legislative elections being held in September. The populist anti-immigration hard right is currently polling at 18-20 percent in the opinion polls.
