BERLIN (Reuters) - Germany will have to go its own way on immigration if it cannot get other European Union states to sign up to migrant return deals, Interior Minister Horst Seehofer said in remarks that could shatter the fragile peace in Angela Merkel’s government.

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Merkel’s government teetered on the brink of collapse for much of last week as Seehofer’s Bavarian conservatives demanded a unilateral tightening of Germany’s border controls that the chancellor was only prepared to concede in the framework of a European agreement.

But in an interview with news magazine Der Spiegel, extracts of which were published on Friday, Seehofer said that if Germany could not seal the promised deals with other EU countries, he would act unilaterally.

“It wouldn’t be a good strategy to assume that there are going to be no bilateral agreements,” he said. “Then we’d have to go back to the plan of turning people away at the border ... starting all over again.”

Merkel, whose decision to open Germany to about a million people seeking asylum in 2015 fueled the rise of anti-immigration parties, rejects unilateral expulsions as going against the spirit of European cooperation.

Seehofer’s restatement of his hard line came a day after the Social Democrats (SPD), the third party in Merkel’s fragile coalition, finally gave their consent to the migration deal after a bruising battle that left lingering resentment.

“After the past days of chaos (within the conservative camp), the interior minister has a lot of work to do,” Burkhard Lischka, an SPD interior affairs spokesman, told the Rheinische Zeitung newspaper.

Seehofer, whose Christian Social Union (CSU) has for decades been in a sometimes fractious conservative alliance with Merkel’s Christian Democrats (CDU), was in Vienna on Wednesday to discuss return agreements with Austrian Chancellor Sebastian Kurz.

The RND newspaper group reported that he hoped to reach a deal on returning to Italy refugees who first registered there by the end of July.

Seehofer, looking to shore up his party ahead of October regional elections in which it faces a stiff challenge from the anti-immigration Alternative for Germany (AfD), has staked his political future on securing tighter controls.