Under Germany's constitution, Merz needs a two-thirds majority to get the changes passed. With the support of the Greens and Social Democrats, he should succeed. Urgent motions by both the AfD and the Left to challenge next week's sessions of the outgoing parliament failed at the constitutional court on Friday, enabling the vote to go ahead.

The country's likely next conservative CDU chancellor Friedrich Merz said cost-cutting must be discussed during coalition talks with the center-left Social Democrats. It comes after he backed a historic spending package.

A new deal with the Greens could allow for as much as €1 trillion in new spending for defense and infrastructure over the next decade.