In a letter titled “a statement from U.S. organizations on the Ukraine crisis,” Biden was asked “to stop escalating the extremely dangerous tensions” between Kyiv and Moscow.

“It is gravely irresponsible for the president to participate in brinkmanship between two nations that possess 90 percent of the world’s nuclear weapons,” said the statement, which was re-released on Tuesday.

The statement said it represented “millions of people in the United States” and was signed by more than 100 groups, including RootsAction.org, Veterans For Peace and Progressive Democrats of America.

It said that for the U.S. and Russia “the only sane course of action now is a commitment to genuine diplomacy with serious negotiations, not military escalation,” which could “easily spiral out of control” and thus push the world to “the precipice of nuclear war.”

“While both sides are to blame for causing this crisis, its roots are entangled in the failure of the U.S. government to live up to its promise made in 1990,” not to expand eastwards.

The groups’ statement echoed the argument made repeatedly by Moscow that the alliance has encroached towards Russia’s border.

At international talks in January, Moscow reiterated its demands, which included Ukraine being blocked from joining NATO and the alliance drawing down its presence by Russia’s borders.

With more than 100,000 Russian troops massed on Ukraine’s borders, Biden has warned that an attack was imminent, although Ukrainian President Volodymyr Zelenskyy has warned against creating panic with talk of an invasion.

Tuesday’s letter said that “rather than dismissing out of hand” Moscow’s demand for a guarantee Ukraine will not join the alliance, “the U.S. government should agree to a long-term moratorium on any NATO expansion.”

Russia has insisted it has no plans to invade Ukraine. The Kremlin, backed by government-friendly media outlets, has pushed the narrative that it is the U.S. and other Western countries—and not Moscow—stoking tensions with talk of war.

Vladimir Dzhabarov, first deputy head of Russia’s Federation Council committee on international affairs, told the newspaper Izvestia that “the conflict between Russia and Ukraine is needed primarily by the Americans as “they will derive certain benefits from it.

“Ukraine, against the backdrop of these tensions is, in fact, alone,” he said, as he called on Zelenskyy to negotiate with the leaders of the self-proclaimed Donetsk and Luhansk People’s Republics in the Donbas region, where conflict has been ongoing since 2014.

The breakaway republics have stepped up their claims that Ukrainian armed forces are gearing up for offensive operations in the Donbas.

“If there is a provocation, perhaps without Zelenskyy’s knowledge,” Dzhabarov said, “then a conflict may break out, the consequences of which will be severe for both peoples.”

Newsweek has contacted the White House for comment.