UNITED NATIONS (AP) — Russia late Friday blocked agreement on the final document of a four-week review of the U.N. treaty considered the cornerstone of nuclear disarmament.

It’s widely believed that Russia objected to the report’s criticism of its military takeover of Europe’s largest nuclear plant soon after Russian troops invaded Ukraine, an act that has raised fears of a nuclear accident.

Igor Vishnevetsky, deputy director of the Russian Foreign Ministry’s Non-Proliferation and Arms Control Department, told the delayed final meeting of the conference reviewing the 50-year-old Nuclear Nonproliferation Treaty that “unfortunately, there is no consensus on this document.” He insisted that many countries — not just Russia — didn’t agree with “a whole host of issues” in the 36-page last draft.

The document needed approval by all 191 countries that are parties to the treaty aimed at curbing the spread of nuclear weapons and ultimately achieving a world without them.

Argentine Ambassador Gustavo Zlauvinen, president of the conference, said the final draft represented his best efforts to address divergent views and the expectations of the parties “for a progressive outcome” at a moment in history where “our world is increasingly wracked by conflicts, and, most alarmingly, the ever growing prospect of the unthinkable nuclear war.”

But after Vishnevetsky spoke, Zlauvinen told delegates, “I see that at this point, the conference is not in a position to achieve agreement on its substantive work.”

The NPT review conference is supposed to be held every five years but was delayed because of the COVID-19 pandemic. This marked the second failure of its state parties to produce an outcome document. The last review conference in 2015 ended without an agreement because of serious differences over establishing a Middle East zone free of weapons of mass destruction.

Those differences haven’t gone away but are being discussed, and the draft outcome documents obtained by The Associated Press would have reaffirmed the importance of establishing a nuclear-free Mideast zone. So, this was not viewed as a major stumbling block this year.

The issue that changed the dynamics of the conference was Russia’s invasion of Ukraine, which brought Russian President Vladimir Putin’s warning that Russia is a “potent” nuclear power and that any attempt to interfere would lead to “consequences you have never seen.” He also put Russia’s nuclear forces on high alert.

Putin has since rolled back, saying that “a nuclear war cannot be won and must never be fought,” a message reiterated by a senior Russian official Aug. 2, the opening day of the NPT conference.

But the Russian leader’s initial threat and the occupation of the Zaporizhzhia nuclear plant in southeastern Ukraine as well as the takeover of the Chernobyl nuclear plant, scene of the world’s worst nuclear disaster in 1986, renewed global fears of another nuclear emergency.

Earlier this week, the U.S. ambassador to the U.N., Linda Thomas-Greenfield, told the Security Council that the Biden administration was seeking a consensus final document that strengthens the nuclear treaty and acknowledges “the manner in which Russia’s war and irresponsible actions in Ukraine seriously undermine the NPT’s main purpose.”

Russian Ambassador Vassily Nebenzia accused the United States and its allies at that council meeting of “politicizing the work on the final document, putting their geopolitical interests in punishing Russia above their collective needs in strengthening global security.”

“Against the backdrop of the actual sabotage by the collective West of the global security architecture, Russia continues to do everything possible to keep at least its key, vital elements afloat,” Nebenzia said.

The four references in the draft final document to the Zaporizhzhia plant, where Russia and Ukraine accuse each other of shelling, would have had the parties to the NPT express “grave concern for the military activities” at or near the facility and other nuclear plants.

It also would have recognized Ukraine’s loss of control and the International Atomic Energy Agency’s inability to ensure the plant’s nuclear material is safeguarded. It supported IAEA efforts to visit Zaporizhzhia to ensure there is no diversion of its nuclear materials. The agency’s director is hoping to organize such a visit in coming days.

The draft expressed “grave concern” at the safety of Ukraine’s nuclear facilities, in particular Zaporizhzia, and stressed “the paramount importance of ensuring control by Ukraine’s competent authorities.”