The money earmarked for modernizing the US nuclear arsenal would go toward upgrades to the W76, B61, W78 and W88 nuclear weapons, as well as toward the construction of a uranium processing facility in Tennessee and “sustaining the existing stockpile by maintaining the underlying science, surveillance and other support programs,” according the proposed budget.

The budget proposals come as no surprise given the pressure Republican lawmakers put on Obama to modernize the US nuclear arsenal in exchange for their support for New START, which was ratified by the US Senate in December 2011, said Simon Saradzhyan, a security expert at Harvard University’s Belfer Center for Science and International Affairs.

“Russia is modernizing, and other countries are actually expanding their arsenals,” Saradzhyan told RIA Novosti on Wednesday. “The United States is not unique in doing this.”

Nonproliferation advocates this week expressed concern over a report by the Center for Public Integrity (CPI) ahead of Wednesday’s budget unveiling that outlined planned budget cuts for programs aimed at preventing nuclear materials from falling into the wrong hands.

“[T]he U.S. programs for securing, reducing and eliminating weapons usable nuclear materials are a critical part of our strategy for combating nuclear terrorism and preventing the proliferation of these deadly dangerous materials,” Joan Rohlfing, president of the Nuclear Threat Initiative, was quoted by CPI as saying Wednesday.

“A decision to significantly cut these programs, including our near-term ability to dispose of excess plutonium, would be a setback to our ability to reach critical security goals,” Rohlfing added, CPI reported.

Saradzhyan said that the nonproliferation cuts targeting the Mixed Oxide (MOX) Fuel Fabrication Facility, which is being built in South Carolina and has been plagued by cost overruns, would not impact nuclear security.

The facility would dispose of plutonium by converting it to MOX fuel and burning it in commercial nuclear reactors.

“The materials that would be processed there are not currently threatened, meaning it is not like there is no plausible possibility that these materials will be stolen by a group and fashioned into a nuclear device,” he told RIA Novosti.

Saradzhyan added that he does not think it would be wise to slash funding for efforts to secure and retrieve weapons-grade materials in other countries.

“Lack of these materials is the biggest obstacle that terrorists face in building nuclear weapons,” he told RIA Novosti.