Demand for Tighter Border Threatens to Undo German Government

Chancellor Angela Merkel faces Monday deadline to defuse immigration challenge from interior minister

BERLIN—German Chancellor Angela Merkel’s ruling conservatives are holding last-ditch talks this weekend to defuse an escalating dispute over immigration and avert a breakup of her government.

Horst Seehofer, who is Ms. Merkel’s interior minister and a party leader in her fragile coalition, has threatened to ignore a veto by the chancellor and forge ahead next week with a plan to turn away some migrants at the German border.

Doing...