The US National Nuclear Security Administration (NNSA) has called for a tenfold increase in the levels of "plutonium equivalent" material stored at a New Mexico nuclear facility to allow for the resumption of plutonium pit production.

The call has alarmed nuclear watchdog groups.

If approved, the increased production of plutonium pits - the core of nuclear weapons - would occur at New Mexico's Los Alamos National Laboratory, a nuclear weapons facility, the NNSA said on Thursday.

It would raise levels of "plutonium equivalent" material stored at Los Alamos from 38.9 to 400 grams.

The NNSA made the call in an environmental assessment review, a study on the impact of a particular project that is meant to show compliance with US environmental regulations.

The public will now have 30 days to comment on the environmental assessment.

Pits, named after the hard centres found in fruits such as peaches or plums, are "critical" to nuclear weapons, according to the NNSA. They are about the size of a grapefruit.

The Department of Energy plans to increase plutonium pit production to 30 pits annually until 2030 when the number will be ramped up to 80.

Pit production was stopped in 2011.

Cost to the budget and environment

Watchdog groups expressed concern over risks to the environment and budgetary requirements needed for the increase.

Nuke Watch New Mexico, a group that tracks environmental and budgetary oversight in US nuclear weapon facilities, questioned the need for the increase in a statement provided to Al Jazeera.

The US already has "some 15,000 pits" stored at a facility in Texas, the group said.

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Nuclear Watch Director Jay Coghlan said that instead of an increase, "there should ... be a programmatic review of all aspects of expanded plutonium pit production, including the inevitable cost overruns, nuclear safety problems, and contamination".

The expanded amount of radioactive materials has already required a $2m upgrades for facilities at Los Alamos, which recently reopened after a three-year closure over safety concerns.

The Trump administration, which has taken an aggressive stance towards the use of nuclear weapons, requested an additional $210m for continued plutonium management at Los Alamos, according to the Los Alamos study group.

The group also warned that increasing plutonium pit production to 80 cores annually is estimated to cost roughly $8bn more.

The pit holds the radioactive materials - either uranium, plutonium, or a mixture of both depending on the type of weapon - which reach critical mass after the detonation of other explosives, causing a nuclear blast.

In 1992, the Rocky Flats Plant, which produced replacement pits for the US nuclear stockpile, closed on the orders of then-President George HW Bush.

The closure came after Rockwell International, the company contracted to run the site, was found to have violated work safety and environmental laws.

The NNSA recouped its losses in 2007 when New Mexico's Los Alamos National Laboratory became capable of producing the pits following upgrades to the facility.

Nuclear tensions

The Los Alamos Study Group Director Greg Mello said the Trump administration is using ongoing tensions with Russia to justify spending on the nuclear stockpile.

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The two nations were nuclear adversaries during the Cold War when the Soviet Union and the US rushed to produce equivalent levels of warheads in a policy known as "mutually assured destruction".

In the late 1980s, the US and USSR had between 30,000 and 40,000 nuclear warheads.

The two countries signed the international Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1968, which aims to limit the spread of such arms.

Following the dissolution of the USSR in 1991, the US and Russia undertook a disarmament campaign.

The US currently holds roughly 6,600 nuclear warheads, while Russia's stockpile sits at 6,800, according to estimates from the Federation of American Scientists, an anti-proliferation group.

The US does not produce "new" nuclear weapons, but existing warheads undergo extensive and costly "life extension" upgrades, resulting in a modernised arsenal.

Mello said in a statement that the US government should respect the environment and its own budget by employing "NPT-compliant disarmament for a change, not assuring mutual destruction forever".