President Biden pledged to kill Europe’s Nord Stream 2 gas pipeline if Russia invades Ukraine. Can he really do that?

That’s the big question after a press conference Monday from Joe Biden and Olaf Scholz, in which the U.S. president gave a definitive pledge to kill the project under such circumstances—and the German chancellor did not, though he certainly didn’t say that was off the table.

Here’s a quick rundown of what Nord Stream 2 is, what was and wasn’t said on Monday, what Biden can (and can’t) do, and why the two crucial Western leaders don’t appear to be on the same page.

Nord Stream 2

Nord Stream 2 is the second phase of an existing and operational Nord Stream gas pipeline that runs under the Baltic Sea, from western Russia to northern Germany. It effectively doubles the capacity of the original pipeline.

Germany has always backed it, obviously, but the rest of Europe less so, because of two main reasons. Firstly, it is seen as increasing Europe’s energy dependence on an increasingly hostile Russia—Europe already gets around 40% of its natural gas from Russia, and in Germany the proportion is over half.

Secondly, it will make it easier for Russia to bypass Ukraine—which it invaded in 2014, illegally annexing Crimea—when sending gas to Europe. At the very least, this could be used to deprive Ukraine of valuable transit fees. The U.S. has also been deeply and fairly consistently opposed to the project for these reasons, since the Obama administration.

U.S. opposition to Nord Stream 2, expressed in the form of highly targeted sanctions on companies involved in the scheme, initially held up its completion. It was finally finished after the U.S. and Germany reached a deal in mid-2021, in which Germany promised to “limit Russian export capabilities to Europe in the energy sector” in the case of Russian aggression toward Ukraine. However, the pipeline is still not operational, because the German energy regulator has delayed its certification on bureaucratic grounds (the Nord Stream 2 operating company needs to be incorporated in Germany first).

Now, Russian troops are massing near the Ukrainian border.

Who said what on Monday?

After they met Monday, Biden and Scholz were asked whether the latter had given the former any assurances about Nord Stream 2 in the event of a Russian invasion of Ukraine.

Biden: “We will bring an end to it. The notion that Nord Stream 2 is going to go forward with an invasion by the Russians—that’s not going to happen.”

Scholz: “We are acting together. We are absolutely united—and we will not take different steps. We will do the same steps, and they will be very, very hard to Russia, and they should understand.”

Biden’s words were unequivocal and quickly led to a rise of around 4% in European gas futures. Scholz’s words were relatively tough for a man who has long held off from saying anything definitive about the subject, but he didn’t even mention Nord Stream 2 by name.

Could Biden kill the pipeline?

That’s unclear. The U.S. could in theory reinstate the earlier sanctions on companies involved in the pipeline, or create new ones. Republican Sen. Ted Cruz sponsored a bill to do just that, but it failed in a mid-January vote. While several Democratic senators joined Republicans in support of the bill, the final 55–44 tally fell short of the 60 votes needed to pass.

The Biden administration opposed the bill on the grounds that it would remove leverage the U.S. had over Russia and harm relations with Germany. Even Democratic Sen. Jeanne Shaheen—who had previously cosponsored Nord Stream 2 sanctions with Senator Cruz—voted against it, saying it would “drive a wedge” between the U.S. and European allies, especially Germany.

The Biden administration would clearly prefer Germany to take the lead on the issue, and for Chancellor Scholz to unequivocally state the pipeline is dead if Russia invades.

So what gives?

Scholz’s fence-sitting is not novel in German politics—Angela Merkel’s administration (in which Scholz served as finance chief and deputy chancellor) was also notably wishy-washy on the question of Nord Stream 2. Generally speaking, it is also legendarily difficult to get a definitive answer out of the man, who prefers the sort of bland, robotic pronouncements that earned him the nickname of “Scholzomat.” But, with war being a distinct and imminent possibility, why can’t Scholz finally take a stand?

According to Joachim Krause, academic director of the Institute for Security Policy at Kiel University, the answer likely lies in Scholz’s Social Democratic Party (SPD).

“It might be he has in mind his own party, which is firmly behind the Nord Stream project—at least many people in his party,” Krause told Fortune Tuesday. “Maybe he doesn’t want to bear the responsibility. It might be he has already accepted that Nord Stream will be killed, but on the other hand he doesn’t want to get blamed for it.”

The SPD’s stance is based on several factors. For one thing, Gerhard Schröder—the last SPD chancellor before Scholz—has spent his post-political career cozying up to the Kremlin. Schröder is chair of Nord Stream 2 and an independent director at Russian oil producer Rosneft, and was last week nominated to join the board of directors at Gazprom, Nord Stream 2’s parent.

However, Krause thinks the Schröder aspect of the situation has been overblown, as the former chancellor has little influence in Germany these days. The security-policy expert sees greater sway coming from figures such as Manuela Schwesig, the SPD minister-president of Mecklenburg-Vorpommern, the state where Nord Stream 2 hits German land. After all, the project comes with jobs.

But above all, Krause points to the Social Democrats’ ideological orientation in recent decades. “The SPD has so much put their eggs in the basket of peace policy, in which everything can be solved by dialogue and arms control, and economic connectivity will promote peace,” he says. “This is the basic thinking, and it is hard to convince the Social Democrats that this is the wrong approach to deal with Russia.”

Much the same goes for the Greens who are junior members of Germany’s governing coalition. Even if Green Foreign Minister Annalena Baerbock is relatively critical of Russia, her party is, like today’s SPD, the product of the peace movements of the 1980s. Krause says this philosophy is behind not only Germany’s Nord Stream 2 stance, but its refusal to send arms to Ukraine, beyond a meager 5,000 helmets that prompted Kyiv Mayor (and former boxing champ) Vitali Klitschko to quip: “What will Germany send next? Pillows?”

Could that change?

According to Krause, it “might not be that easy” for the German government to kill the project, for legal reasons such as the threat of compensatory lawsuits. New legislation might do the trick, but, he said, “many in Berlin are hoping the European part of the process might stop the whole thing.”

The European Commission did indeed step in at the end of January, announcing that Nord Stream 2 was on hold while it reviews the project’s compliance with EU energy policy. “Clearly there is certain action from [the] Russian side that triggered the European Commission’s investigation whether Gazprom is in this situation acting in line with market principles,” said Commission Vice President Valdis Dombrovskis at the time.

Whatever happens now, in the longer term Germany does hope to wean itself off Russian gas, in favor of greener alternatives such as hydrogen. As Scholz said in a Monday CNN interview: “Germany will go out of the use of gas and oil and coal within 25 years, so we will not depend on the import of fossil fuels to Germany anymore.”

Right now, though, Scholz’s administration seems to be taking damage from its handling of the Nord Stream 2 issue, along with others such as the COVID-19 pandemic and inflation. According to recent Infratest polling, support for the SPD has slipped by four percentage points since December, with the beneficiaries being the out-of-power Christian Democrats. And within the past month, Scholz’s own approval rating fell from 60% to 43%.

That said, a majority of Germans still think Nord Stream 2 should go ahead, with support being particularly high (71% versus a national average of 57%) in former communist East Germany. In that light, and considering the potential impact on consumer energy prices, it’s not hard to see why Scholz and his government would rather leave any painful decisions until the moment when they absolutely have to be made.