BERLIN — Germany’s would-be next chancellor, Friedrich Merz, is asking lawmakers Tuesday to allow the country to put “whatever it takes” into defense as doubts mount about the strength of the trans-Atlantic alliance, and to authorize an enormous fund for investment in its creaking infrastructure, financed by hefty borrowing.

The outgoing parliament is set to meet for a final time to vote on the plans as Merz’s center-right Union bloc works to put together a governing coalition with the center-left Social Democrats of outgoing Chancellor Olaf Scholz after winning last month’s election.

The plans will need a two-thirds majority in parliament’s lower house, the Bundestag, because they involve changes to Germany’s strict self-imposed borrowing rules — the so-called “debt brake,” which allows new borrowing worth only 0.35% of annual gross domestic product and is anchored in the constitution. That forced the prospective coalition partners into negotiations with the environmentalist Greens, whose votes will be needed to get enough support.

The package would exempt from the debt rules spending on defense and security, including intelligence agencies and assistance to Ukraine, of more than 1% of GDP. It also foresees setting up a 500 billion-euro ($544 billion) fund, financed by borrowing, to pour funding into Germany’s infrastructure over the next 12 years and help restore the economy — Europe’s biggest — to growth.

At the Greens’ insistence, 100 billion euros from the investment fund will go into climate-related spending.

The plans amount to an about-turn for Merz, whose party had spoken out against running up new debt before the election without entirely closing the door to future changes to the “debt brake.” The Social Democrats and Greens had long argued for a reform of the borrowing rules.

Recent weeks have brought new urgency to efforts to further strengthen Germany’s long-neglected military. The outgoing government created a special 100 billion-euro fund to modernize it, which also helped Berlin meet the current NATO target of spending 2% of GDP on defense. But that pot will be used up in 2027, and doubts have grown recently about the Trump administration’s commitment to European allies.

Merz said earlier this month that Germany and Europe must quickly strengthen their defense capability and that “‘whatever it takes’ must also go for our defense now.”

He told ARD television Sunday that “the situation has once again escalated dramatically in recent weeks” and that Germany’s budget had turned out to be in worse shape than previously known.

Of Tuesday’s vote, he said: “It will be close, but it will work.”

“Of course there is still persuasion to be done in all three parliamentary groups, but we should not less this opportunity go unused,” he said.

The package is being brought to the old parliament — rather than the newly elected one, which will hold its first session on March 25 — because parties that are unlikely to agree have just over one-third of the seats in the new chamber. The far-right Alternative for Germany portrays itself as a staunch defender of the “debt brake,” while the Left Party opposes it but is skeptical about military spending.

In the outgoing Bundestag, the Union, Social Democrats and Greens have a combined 520 of the 733 lawmakers — 31 more than are required for a two-thirds majority.

If the package is approved Tuesday, it faces another hurdle Friday in parliament’s upper house, which represents Germany’s 16 state governments. They are also set to be given more freedom to borrow money.

A two-thirds majority will also be needed in the upper house. That initially was uncertain because the parties behind the plans control only 41 of the 69 upper-house votes. But on Monday, the conservative-led governing coalition in Bavaria, which has six votes, also agreed to support the package.