Congressional Progressive Caucus Chair Pramila Jayapal, D-Wash., is leading a group of Democrats in pushing back on President Joe Biden’s plans to continue spending exorbitant sums on an expanding nuclear arsenal.

“We write today to express our grave concern that your Fiscal Year 2022 budget proposal for nuclear weapons does not reflect your longstanding efforts to reduce our reliance on nuclear weapons,” Jayapal and 28 Democratic colleagues wrote Biden today in a letter obtained by The Intercept. (In 2010, Biden led the White House’s efforts to convince the Senate to approve the New Strategic Arms Reduction Treaty. The treaty, which passed with a bipartisan majority, reduces the U.S. and Russia’s deployment of nuclear weapons.)

Their letter comes months after Biden caused alarm among progressives and the arms control community by proposing a defense budget that funded nuclear weapon programs initiated by the Trump administration that the Obama administration had deemed unnecessary. The budget also increased funding to develop highly controversial missiles started under President Barack Obama.

The stakes couldn’t be higher as the U.S. continues to grow its nuclear arsenal with an array of new warheads, bombs, cruise missiles, intercontinental ballistic missiles, and delivery vehicles, which activists warn increase the risk of nuclear war. Meanwhile, as Democrats face accusations of hiking the deficit to fund significant investments in health care, family benefits, and clean energy, the Congressional Budget Office has estimated Biden’s FY-22 budget proposal would result in costs of $634 billion over 10 years.

Jayapal and her colleagues see an opening for Biden to reverse course as the president works on crafting a nuclear weapons strategy to replace the Trump administration’s. “We respectfully urge you to use the forthcoming Nuclear Posture Review (NPR) to set a nuclear strategy that aims to limit the role of nuclear weapons in our national security, reduces unnecessary spending, and sets the stage for progress towards your recent agreement with Russian President Vladimir Putin to pursue additional arms control and risk reduction measures,” they wrote.

They specifically call out Biden for his administration’s request for funds to develop a new high-yield submarine-launched ballistic missile warhead known as the W93 that Donald Trump greenlighted and for his plans to maintain the B83 gravity bomb, which has an explosive yield up to 100 times larger than the bomb dropped on Hiroshima. The Obama administration had opposed these initiatives, they note, but Biden is now continuing them. (Obama Energy Secretary Ernest Moniz pledged to retire the B83 since the government is replacing it with the B61-12 bomb.)

Jayapal and her colleagues also explicitly call on Biden to cancel the Long-Range Standoff Weapon, a new nuclear air-launched cruise missile initiated under Obama. The CPC chair had proposed an amendment to the FY-20 Defense Appropriations Act that would have zeroed-out funding to develop the weapon, but it failed in a 138-289 vote back in 2019.

The letter stops short of calling on Biden to cancel the land-based leg of the nuclear triad — a redundant and especially dangerous part of the triad — which the Defense Department is currently modernizing. Perhaps the most controversial new nuclear weapon program, the Ground Based Strategic Deterrent will replace the Cold War-era Minuteman III intercontinental ballistic missile system starting in 2029. The lawmakers instead appear to endorse a proposal by California Democrat John Garamendi, one of the signers, to halt the new system and instead extend the service life of the legacy weapon.

“Taking these initial steps to slow the development of new nuclear weapons will increase the day-to-day security of the United States and our allies, set the stage for potential progress in future talks on arms control, and save billions of dollars for more pressing needs,” they wrote.

Jayapal and her colleagues don’t state whether they’ll use their leverage as a bloc to gain concessions, though. They could threaten, for example, to withhold support for the annual defense authorization or appropriation bills that will come to the House floor later this year.

House Armed Services Committee members Sara Jacobs, D-Calif., and Ro Khanna, D-Calif., who signed the letter, took this drastic step during a markup of the defense authorization bill last week. Deeply opposed to the panel’s decision to add $24 billion onto Biden’s $715 billion FY-22 budget, the two lawmakers voted against advancing the bill to the House floor.