BERLIN (Reuters) - The leader of Germany’s center-left Social Democrats on Friday said she cannot rule out the collapse of Chancellor Angela Merkel’s fragile coalition government if it runs into another divisive dispute such as its recent fight over migration.

FILE PHOTO: Andrea Nahles, leader of Social Democratic Party (SPD) arrives for a coalition meeting with the CDU and the SPD parties at the Reichstag in Berlin, Germany, July 5, 2018. REUTERS/Axel Schmidt

Andrea Nahles told the RND German newspaper chain that the battle over migration between Merkel’s conservative Christian Democratic Union (CDU) and its CSU Bavarian ally had frustrated many, including her party, because it was an internal squabble and not focused on substantial issues.

Asked if a further dispute could undo Merkel’s “grand coalition,” Nahles said: “After the experiences of the last months, I can’t exclude that. It was serious.”

Merkel’s government was brought to the brink of collapse over strident demands from Interior Minister Horst Seehofer, who leads the Bavarian conservatives, that Germany’s migration policy be tightened up.

The clash has further eroded support for the ruling parties, a new poll conducted by broadcaster ARD showed on Thursday.

Annegret Kramp-Karrenbauer, general secretary of Merkel’s CDU, said the declining poll numbers reflected the impact of the fight over migration within the conservative bloc.

“In the end, the way we fought with each other left only losers. It hurt all of us,” she told the Rheinische Post newspaper. “We have to talk about it again, and work through it in both parties.”

Nahles called for Seehofer to stop carrying out what she dismissed as “pseudo debates”.

“There are important challenges facing him - an immigration law, integration (of new migrants) and new housing construction,” Nahles said.

Seehofer on Friday said he plans to start using Twitter to take his message directly to the people ahead of an election in the state of Bavaria in October in which the CSU could lose its absolute majority in the region.