Iran’s continued blocking of access by international inspectors to a facility making centrifuge parts for uranium enrichment will seriously affect prospects for negotiations over the Iran nuclear deal scheduled to resume next week in Vienna, the head of the International Atomic Energy Agency said Wednesday after high-level talks.

IAEA Director General Rafael Grossi told member states that his discussions in Tehran had “proved inconclusive” and that he could not provide negotiators with “essential,” up-to-date information about some aspects of Iran’s nuclear activities.

Even before Grossi’s efforts, Western participants in the Vienna negotiations had grown increasingly pessimistic about a successful outcome and held meetings to decide what they would do if they fail.

The Biden administration has insisted it far prefers a diplomatic outcome, but that it is prepared for the worst.

If Iran “doesn’t want to get back into the deal, if it continues to do what it appears to be doing now, which is to drag its feet at the nuclear diplomatic table and accelerate its pace when it comes to its nuclear program, if that’s the path it chooses, we’ll have to respond accordingly, chief U.S. negotiator Robert Malley said in an interview with NPR.

“The options that are at America’s disposal are, you know, they’re familiar to all,” Malley said.

Most immediate options include additional sanctions. Although there are few U.S. measures that have not been levied, the Americans see European partners as being more willing to implement “snapback” measures on broader international sanctions that were lifted as part of the original deal.

While prepared to respond to Iranian military provocations, the administration has tried to persuade Israel, which is thought to be responsible for attacks against Iranian facilities, to hold off.

One of those attacks was at a centrifuge production facility in Karaj, a city near Tehran, where IAEA monitoring cameras were destroyed last summer. Grossi’s negotiations centered on gaining Iranian agreement for the cameras to be restored.

After six sessions beginning in April, Iran suspended the Vienna negotiations in June after it elected a new government that has adopted, at least rhetorically, a much harder line.

Across the table from Iran are Britain, Germany, France, Russia and China — all original signers of the 2015 agreement under which Tehran agreed to limit the quantity and quality of its uranium enrichment and curtail other activities in exchange for the lifting of economic sanctions and other relief.

President Donald Trump withdrew the United States from the agreement in 2018, reinstating sanctions that had been removed and imposing hundreds of new ones as part of a “maximum pressure” campaign designed to crush the Iranian regime.

In response, Iran first gradually — and in recent months rapidly — exceeded the limits it had adhered to, producing and operating more, and far more sophisticated, centrifuges that enrich uranium to a level that has now reached 60 percent.

That is close to what is required to produce bombmaking fissile material.

Administration officials this week confirmed assessments by nongovernmental experts that Iran’s “breakout time” for enough material for one weapon has moved from about a year when Trump withdrew from the deal, to what may now be only a few weeks.

Iran has long denied that it has any interest in producing nuclear weapons, saying its activities are for research and nuclear power purposes.

Iran has refused to meet directly with the United States, saying it is no longer a party to the accord. Instead, the European signers have served as go-betweens in the negotiations, transmitting information between U.S. and Iranian officials in separate Vienna hotel rooms.

President Biden campaigned on a pledge to return to the nuclear agreement, called the Joint Comprehensive Plan of Action, or JCPOA.

The administration has said its initial goal is “compliance for compliance,” in which both Iran and the United States would return to the original terms of the deal, while expecting that would provide a platform for ongoing discussions about other issues, including Iran’s ballistic missile program and the country’s support of regional proxy wars and terrorism.

During the first six rounds, U.S. and European officials felt they had made progress on many of the specific, simultaneous steps both sides would take, and could quickly come to a resolution.

But the new Iranian government refused to set a date for a seventh meeting, while insisting that all sanctions against it be lifted — not just the ones that apply to its nuclear program, per the original agreement — and that the United States would guarantee that no future administration would again withdraw.

Administration officials have said they will not comply with the first condition and cannot agree to the second.

As Iran has expanded its nuclear activities, the United States and its European allies have warned that those moves may reach a point where the original terms of the deal might no longer apply.

Last month, Iran announced that it was prepared for talks to reconvene on Nov. 29.

But Western participants say they remain in the dark about whether Iran’s new government will approach the meeting as the seventh in a series or jettison provisional agreements already reached and expect to begin anew.

Along with the lack of agreement with the IAEA this week, Iran’s “very hard-line positions about their demands [don’t] augur well for the talks,” Malley told NPR.

The administration played down reports that it might be willing to forge a temporary agreement on “confidence-building” measures, including a partial lifting of some sanctions in exchange for a freezing of some Iranian activities, to provide more time for negotiations.

“We have been very clear that we are not prepared to take unilateral steps solely for the benefit of greasing the wheel,” State Department spokesman Ned Price said Tuesday. “We are prepared to engage in a mutual return to compliance with the JCPOA. . . . And we hope that we see the same seriousness of purpose from the Iranians when they return to Vienna next week.”