By Thomas Escritt and Jörn Poltz
BERLIN/MUNICH (Reuters) - German Chancellor Angela Merkel's conservative Bavarian allies agreed to give her two weeks' breathing space on Monday to find a European solution to a row over immigration that threatens to scupper her three-month-old coalition government.
Bavaria's Christian Social Union (CSU), anxious about losing votes to a new right-wing party in an October regional election, wants a ban on admitting migrants into Germany who have already registered in another EU country. Merkel opposes such a ban.
U.S. President Donald Trump, defending his own tough anti-immigrant polices, waded into Germany's debate on Monday with a series of tweets criticizing Merkel's open-border policy as a "big mistake" that had fueled crime in Europe.
The CSU leadership agreed at a meeting in Munich to delay introducing their entry ban until after a June 28-29 European Union summit, allowing Merkel time to seek an EU-wide solution.
Merkel opposes any unilateral move by Interior Minister Horst Seehofer, who is also CSU chairman, that would reverse her 2015 open-door policy on migrants and undermine her authority. Monday's compromise means he can introduce immediate expulsion for one subset of migrants.
"We wish the chancellor much luck," Seehofer told a news conference in Munich, announcing that he would nonetheless issue orders for people who have already been expelled to be turned back at the borders.
"This is not about winning time or anything like that but rather that in July, if there is no result at European level, we must implement this - that is a question for the functioning of our constitutional state," he added.
Germany's migration row mirrors squalls seen across Europe since Merkel's decision in 2015 to open Germany's borders to more than a million migrants fleeing wars in the Middle East, transforming the demographic landscape almost overnight.
The CSU hopes its tough line will help it see off a challenge from the anti-immigration Alternative for Germany (AfD) party in wealthy Bavaria's October election.
Trump's tweets attacking Merkel's policy highlighted the emblematic role Germany has come to play in global debates on migration.
"The people of Germany are turning against their leadership as migration is rocking the already tenuous Berlin coalition," he wrote. "Crime in Germany is way up. Big mistake made all over Europe in allowing millions of people in who have so strongly and violently changed their culture!"
Overall, crime in Germany is at record lows, though recent immigrants have contributed to increases in certain categories of crime. Polls show Merkel and her coalition enjoy broad support among voters.
Federal Interior Ministry data shows the number of new arrivals in Germany seeking asylum fell 33 percent on the year to 186,000 in 2017, down from 280,000 the previous year and 890,000 in 2015, at the peak of the migrant crisis.
Merkel, the EU's longest-serving leader, welcomed Monday's compromise in a dispute that has threatened to unravel her new coalition, and said her Christian Democrat (CDU) party would decide how to proceed after the two-week deadline elapsed.
"The CDU and the CSU have the common goal of better organizing and steering immigration into our country and significantly reducing the number of people entering this country," she said.
"A situation like 2015 cannot and will not be repeated."
But she reiterated her opposition to Germany unilaterally closing its borders as this would pass the migrant burden on to neighboring countries, "unleashing undesired domino effects".
A split with the CSU, their ally of seven decades, would deprive the CDU of the governing majority it commands in the Bundestag lower house in coalition with the Social Democrats (SPD). It would also gravely weaken the CSU, whose dominance of Bavarian politics relies on its influence in Berlin.
Perhaps reflecting that nervousness, Seehofer later added: "Nobody wants the end of the coalition, a collapse of the alliance or the fall of the government."
Merkel would still have options if the CSU quit the coalition: Greens leader Annalena Baerbock refused on Monday to rule out replacing the CSU in Merkel's coalition. "If we're in a talks situation in a few weeks, we'll talk," she said.
Merkel later on Monday met Italian Prime Minister Giuseppe Conte for talks in Berlin and said Berlin wanted to support Rome in its efforts to reduce the number of migrants arriving on its shores, possibly handling asylum requests for the European Union in non-European countries including Libya.
Matteo Salvini, interior minister in Conte's anti-establishment government that took office this month in Rome, has adopted a policy of blocking foreign humanitarian boats from Italian ports, which has triggered heated exchanges with France and the Netherlands
Conte called on the EU to change its position on migration and adapt current EU asylum guidelines in favor of "a new approach that is more harmonious, so that whoever sets foot in Italy, sets foot in Europe".
The European Commission has voiced confidence that EU leaders could agree at a summit next week on handling migrants and refugees, but some diplomats were much less optimistic.
(Additional reporting by Paul Carrel, Tom Koerkemeier, Michael Nienaber; Editing by Gareth Jones and Alison Williams)