BERLIN—German Chancellor Angela Merkel’s ruling partners are reconsidering their support for a decadesold arrangement that puts Germany under the U.S. nuclear shield, a development that could further undermine the country’s already-tense relationship with the Trump administration.
The center-left Social Democrats, or SPD, have appointed a commission to re-evaluate their positions on strategic, foreign and security policy, including the merits of “nuclear sharing,” a Cold War-era agreement under which German warplanes would be used to launch U.S. nuclear weapons in case of a Russian attack on Europe, a senior party official said.
The deliberations came partly as a result of President Trump’s withdrawal from a treaty with Russia that regulates the presence of nuclear missiles in Europe, according to SPD officials. The U.S. plans to withdraw from the Intermediate-range Nuclear Forces Treaty after accusing Russia of violating it for years.
After Mr. Trump’s repeated criticism of the military alliance and its members, the SPD move shows NATO’s cohesion is now also under threat from a backlash among center-left forces in Europe that had long stopped questioning the alliance.
Ms. Merkel’s party is continuing to back the agreement. Nevertheless, a decision by its junior coalition partner to oppose nuclear sharing would be momentous, putting into question an institution that is as old as Germany’s 1955 membership of the North Atlantic Treaty Organization.
Consecutive U.S. administrations have criticized Germany for what they called insufficient military spending, but the dispute has escalated under Mr. Trump, who has put Berlin under notice to boost its defense budget.
Parties critical of Mr. Trump tap a rich political vein in Germany. A 2018 Pew Research Center survey for the Munich Security Conference, a global security forum, showed only 10% of Germans thought the U.S. president was doing the right thing regarding world affairs, compared with 35% for Russian President Vladimir Putin and 30% for Chinese President Xi Jinping.
The appointment of the SPD commission will also put additional stress on Ms. Merkel’s fractious coalition. The chancellor’s conservatives back higher military expenditure and want to renew the ailing German air force with an order of U.S.-made aircraft that are certified to carry U.S. nuclear weapons. Leading SPD figures have said they would block the purchase of up to 45 Boeing Co.-made F/A-18 jets recently proposed by Ms. Merkel’s defense minister.
A spokesman for Ms. Merkel said the government would continue to back nuclear sharing, adding that it saw “no reason to debate this aspect of NATO deterrence. We continue to fully support the defensive nuclear strategy of NATO.”
A NATO spokeswoman said the alliance relied on the capabilities and infrastructure of its members in Europe. “Allied aircraft supporting NATO’s nuclear deterrence mission are central to this effort and we welcome the broadest possible participation in our nuclear burden-sharing arrangements,” she added.
Asked about the policy review, U.S. Ambassador to Germany Richard A. Grenell said, “NATO’s nuclear forces are there for deterrence and defense. This is a commitment the alliance has made together. Germany should live up to its commitment.”
Germany is part of NATO’s so-called nuclear-sharing agreement that goes back to the 1950s. While exact numbers are secret, experts believe U.S. has around 180 B61 tactical nuclear bombs on the continent—some 20 in Germany and the rest spread across Belgium, Italy, the Netherlands and Turkey.
“We don’t think that the nuclear-sharing agreement is fit for the times anymore,” said Ralf Stegner, vice chairman of the SPD, following a meeting of the party leadership on Monday. He said the SPD was extremely unlikely to support the F/A-18 purchase.
The procurement would be a key step in maintaining nuclear sharing in coming decades. The only aircraft in the German fleet currently certified by the U.S. to carry nuclear weapons are the German-made Tornados. But some of those are 40 years old and are being retired.
Mr. Stegner added that the mounting U.S. pressure on Germany meant that the country was headed toward a fundamental debate about nuclear armament and military spending of a kind that hadn’t taken place since 1982, when a rebellion within the SPD over the stationing of nuclear weapons in Europe contributed to the ouster of Chancellor Helmut Schmidt.
“Nuclear sharing doesn’t necessarily mean we need to host nuclear weapons,” said Rolf Mützenich, the SPD’s deputy floor leader and speaker on defense policy. Mr. Mützenich said Germany could follow the example of Canada, a NATO ally that doesn’t keep U.S. nuclear weapons on its soil.
Mr. Mützenich said he believed a majority of SPD lawmakers would reject any proposal to purchase new U.S. aircraft, partly because of the large cost. Growing animosity between NATO and Russia and the likelihood of a renewed arms race were all arguments against nuclear sharing, Mr. Mützenich added.
The looming dispute about military doctrine, military spending and procurement is just one of many now rocking Ms. Merkel’s coalition—a government many analysts think could unravel as early as this year.
Peter Beyer, Ms. Merkel’s coordinator for trans-Atlantic cooperation and a member of her conservative party, said nuclear sharing was indispensable. Failure to revamp Germany’s aging fleet of nuclear-capable bombers would make a farce of the country’s commitment to the NATO nuclear deterrent, he said.
“How we can get Putin to disarm if we fail to confront him in any way,” Mr. Beyer said. “This does not help peace but creates instability. Our allies, including the smaller states in Europe, would then have to wonder whether they can still rely on Germany.”
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