How Iran will respond to the U.S. assassination of Maj. Gen. Qassem Soleimani remains a matter of speculation, but one outcome seems almost certain: the end of Europe’s long effort to keep the 2015 Iranian nuclear deal alive.

In interviews Friday, European analysts envisioned a number of baleful results from the killing of the general, who was a national hero and potential political leader in Iran, and whose death Tehran has vowed to avenge.

Among those were the downgrading of diplomacy, the destabilization of Iraq and the further strengthening of Iran’s hard-liners and Iran’s Revolutionary Guard.

But the more immediate threat, they said, was to the nuclear deal negotiated by President Barack Obama in 2015.

President Donald Trump pulled the United States out of the treaty in May 2018, calling it “a horrible one-sided deal that should have never, ever been made,” and imposed punitive new sanctions as part of a “maximum pressure” campaign.

The other signatories — Europe in particular, but also Russia and China — tried hard to preserve the agreement, known as the Joint Comprehensive Plan of Action. And Iran initially said it would adhere to its treaty obligations. But Tehran has since taken a series of steps away from the treaty, and analysts fear it may now renounce all of its obligations.

Tehran’s strategy could become clear in a matter of days, as it had already said that it was about to take another step away from the accord.

There was speculation that Iran would return to enriching uranium at 20%, a major breach of the deal, which the European signatories have warned against, said Ellie Geranmayeh, an Iran expert with the European Council on Foreign Relations.

“This would give Europeans even less breathing room to keep the JCPOA alive until November 2020,” when the world would know whether Trump is re-elected, Geranmayeh said. “It will be very difficult for the Europeans to hold it together.”

After conversations Friday morning with officials in Tehran, she said that “people inside Iran pushing for the diplomatic process the Europeans have been advocating have lost a lot of ground.”

Carl Bildt, the former prime minister of Sweden, said that Europe had been trying to prevent war between Iran and the United States for a decade but that the scope for salvaging the nuclear accord now “is very small, and the scope for diplomacy is extremely limited.”

Still, he said, Iran is likely to be careful on how far it acts beyond the accord, since it has tried to keep the nuclear issue largely separate from its regional battles and interests. “I think their response will be more likely on the kinetic side rather than the nuclear one, at least not more than they were going to do anyway,” Bildt said.