Germany's Greens vowed to block plans by likely next chancellor Friedrich Merz for a massive increase in state borrowing to revamp the military and revive growth but forwarded rival proposals on Monday in a bid for compromise.

German Chancellor-in-waiting Friedrich Merz is open to making concessions to the Greens to secure support for constitutional changes that would unleash hundreds of billions of euros in defense and infrastructure spending.

A massive plan to loosen Germany's debt rules and spend hundreds of billions on defence and infrastructure has run into potentially decisive opposition from the Greens, whose votes in parliament would be essential for passage.